I tried the 900mhz models before. They're good for music, but not TTS annouincement. The transmiter on the one I have stays in "standby" until it detects an audio signal. This results in the first 1-2 seconds of your announcements being cut off. You also have to leave the receiver/speakers on all the time, which means they can pickup inteference. I had mine on appliance modules, which were switched on before a TTS announcement. However, this did not work well. Between the transmitter power-on delay and the X10 delay, I always lost 1-5 seconds of TTS, which usually meant there was no announcement at all. I later ran wires and used an AB8SS instead, which worked flawlessly. If HAL gets something like HS, with the ability to use remote speaker clients, then you would not have to worry about it. I'm actually getting ready to sell my AB8SS becuase I now use the speaker clients to distribute TTS.
If you don't want to run wires, you can use wires you already have. Use the unused pair on your phoneline (if you're not using them) or the TWO unused pairs (brown and blue) on some CAT5 that you already have run. I transmit power over my brown and blue CAT5 pairs and it does not intefere with operation of my network at all.