What would the lowest hardware reqs be for a pc to handle everything

Currently my 24/7 HTPC/Server is a Phenom 8850 running at the low power setting with 1 standard SATA drive and 2 750Gb WD green power drives. It has one internal 2 analog tuner card and also 2 HDHR to give me the option of 4 HD and 2 Analog simultaneous recordings.

I Know I need to get a killawatt tester to see what it is pulling but I was also wondering how small you can go in a processor before compromising its basic duties of streaming video, music and also recording TV before you start pushing the PC beyond what it can do.

I was recording three HD shows the other night and I noticed in one of my recordings that occasionally the screen would get pixelated. Now I don't know if that was due to CPU, network bandwidth, tv signal or Hard drive throughput.

My future build/upgrade I plan to swap out the 2 750Gb drives for 2 WD GP 2 terabyte drives in raid 0 and moving the OS to a small SSD. I think that will help with the HDD throughput. But I still wonder about how much the CPU has an effect on streaming, recording and playing content from the pc.

Would a WHS build with SAGE on it save power and then only have extenders access the data? Currently I use a 360 as an extender.
I'm not sure the processor is the main thing to be concerned here with. I'd look at the power requirements for your tuners, network cards and graphics systems.

1) If you don't need wifi, go ethernet.
2) If you don't need graphics except for local control(make sure that SAGE doesn't use your video processor), go with a laptop motherboard with integrated graphics.
3) Keep the number of USB devices attached to a minimum(go with ps2 mouse, kbd and serial devices instead).
4) Make sure you have all the correct drivers for your devices, and pick devices that support good power management so that your machine can sleep and awake by itself.
5) Only keep as much RAM in the computer as you need. When the computer is alseep this is a significant power usage, you'll save a few watts by cutting the extra gig in many machines.
6) Get a new, mobile, low-power processor. Pick the performance based on what your software requires, prob. not much. Stay away from older designs, the newest low-power processors take much less power than a pentium 4.
I should also add that if you are recording 24/7 on multiple streams and are concerned with throughput, you will be sucking a lot of power. No way around that. The majority of power savings in a HTPC come from the time it is idle. For what you need the most you are going to save with a lower power CPU is a few watts, maybe 20 or 30 if you pick your motherboard carefully. Your setup has too many power-hungry things like compression/encoding tasks, drive read/writes and network activity. If you move your compression to a card(if it is not there already), usually you can reduce the processor a lot and save some power. But I suspect we are not talking much. The power is going to a high-powered machine running 24/7.
Maybe Im wrong here, but you were referring to lowest hardware requirements from a technology perspective right - and not necessarily from a used power standpoint that icellama was addressing?

ie. Minimum system requirements that you could away with w/o sacrificing quality of video, music, etc. ???
Maybe Im wrong here, but you were referring to lowest hardware requirements from a technology perspective right - and not necessarily from a used power standpoint that icellama was addressing?

ie. Minimum system requires ments that you could away with w/o sacrificing quality of video, music, etc. ???

Both really. I want the lowest powered machine capable of doing all those tasks and being left on 24/7.

The tasks being the ability to stream to a minimum of 3 extenders, recording 4 streams at once and the ability to use the machine itself as an HTPC.

Or would it be better to build a low power WHS to handle the recording, storage and streaming and run a low power HTPC as a client. I know I'll need at least one HTPC to do the ripping so I can avoid making multiple trips to the WHS box. And also having the features of an HTPC on my main TV.
I think a lot of it depends on what you use for media. From what I understand SageTV and VMC don't take a whole lot if your recording. I thought I heard someone say SageTV is pretty small as a service when recording.

Your bigger draw is going to be during playback. VMC extenders take a lot of CPU for playback, the more extenders the more CPU you'll need. I've heard quadcore for 3-4 Xboxes. On the SageTV side, the video decoding is done on the extender so I think it uses very little CPU for playback when using the extender.
In general you will minimize your CPU requirements by using all hardware encoding and decoding on your capture cards and extenders. However, if you are running software that is controlling those cards, running multiple read/write operations to your hard drive, and streaming data over your network, a minimal processor will get overloaded pretty quickly.

If you want software compression/decompression, go multi-core and possible multi-proc. Lots of parallel math ops, get as many pipelines going as you can. It is kind of ironic just how terrible windows and x86 are for this kind of work, but the dedicated machines are kind of useless for home use.

If you go with hardware compression/decompression, pay close attention to your IO pathways. Make sure to get gigabit ethernet(and wire your house for it) and a fast enough motherboard to handle it. Also speed up your hard drives. The motherboard and peripheral choice here is more important than the CPU.

But, once again, the power savings of reducing CPU are significant, but pale compared to what you save by getting all of your work done in a few hours, then letting the machine power down until it is needed again.
If you do end up replacing the CPU and motherboard for some reason, make sure the new hardware has good power management abilities. With the right CPU and motherboard combination you can definitely get hardware that will underclock the processor when the system isn't being pushed to save energy.

I just built a new quad core machine (using a Q6600 chip which is 2.4Ghz by default) and installed Windows Server 2008 on it this week. My motherboard monitor claims the CPU is pulling about 15-18 watts under light load at about 1.6Ghz. Of course that is only the CPU, so total wattage is higher. Just for grins I overlocked the chip (to 3.2Ghz) for a brief period of time and under that same light load, the CPU was pulling over 40 watts of power. I quickly went back to stock when I saw that power usage since I don't expect to need the extra horsepower overclocking would provide.