Cables between wall mount and surface mount enclosures

I have an Altronix eFlow 102N16 power supply that is in a wall-mount enclosure. I need to get the output wires (12vdc) to a nearby (five feet or so) Elk recessed enclosure. All of the knockouts in the power supply box are on the tops and sides, none in the back of the box.
 
Any good suggestions (pictures) on how to cleanly/neatly get the wires from the side/top of the box into the wall behind it? The wall is covered with drywall.
 
I'm pretty sure the answer to this follow on question will be "no", but is it okay (whatever that implies) to move the internals from the Altronix box to an Elk box of similar size that can be recessed mounted? It looks like all Altronix PS's are in wall-mount boxes. Maybe because they are not typically used in residential locations, or maybe heat buildup if recessed in a wall is a problem?
 
Thanks,
Ira

Not a good idea to transfer the guts of the power supply to a different enclosure an recess mount it. The power supply is UL listed for use in the enclosure it comes in.  If you move it to something else, it would no longer be considered a UL listed system.  From a technical point of view, you may not care, but your insurance company might should there ever be a fire.
 
The Altronix enclosure has air vents on the side.  If you recess mount it, you'll cut off the air flow. 
 
I can think of a couple of ways to get the wire between the 2 enclosures. 
 
One would be to surface mount an electrical box (e.g. 4" square) with side and rear knockouts next to the Altronix. Connect it to the Altronix with a short piece of conduit.  Run the wire into the box and out the back knockout into the wall.
 
Another way would be to use a 90 degree pull elbow to go from the side of the Altronix directly into the wall.  Not sure if this meets code, though.
 

You can cut a hole in the back of the enclosure with a hole saw or suitable knockout set assuming the sheetrock hole is smaller than the hole within the steel enclosure (acting as a grommet or bushing to the steel). As long as separation is maintained, we're not talking about voiding the UL here (different game with some items).

Removing the guts and installing in a different enclosure is typically a "NO" unless the enclosure is listed for a specific purpose (a very slippery slope for a novice).
 
Cleanly and/or neatly would be a few conduit pieces bent at about a 15-20 degree angle to pass into the stud bay. Flex can also be used (Greenfield) to bridge enclosures. Finish the wall appropriately around them.
 
Pulling elbow (jake) can be used, however PVC is not the suitable material here.