Im building a relatively high/mid end HTPC using an ITX form factor with hopefully a discrete GPU (possibly the 7750 as it seems to be v low power) and a 200W PSU.
My quandry is the CPU - I use Adobe Premiere Pro and sometimes After effects, so the faster the CPU the better.
Id love an i5 3450/70s, is this crazy talk in terms of power requirements?? Basically what is the most efficient CPU, power to 'grunt'?
Why not use a more powerful power supply? It's not as if a 350w power supply constantly sucks 350W from the wall, you know.
As for your question, if you want decent power for video processing any of the Intel Ivy Bridge processors are worth a shot. They have a 77W envelope, as opposed to my Phenom II 1090T which draws around 140W (basically double).
That depends on how many amps the 200w PSU can supply on the 12v rail which the CPU, GPU, fans, hard drives, optical drives draws power from. Using the watts you provided the CPU and GPU uses 115w of the 200w which means they will draw a little over 9.5 amps from the 12v rail. Add in the fans, hard drives, optical drives and the power draw on the 12v rail increases.
I generally recommend a 300w PSU for anything with the HD 7750. 250w if the PSU is high quality like a Seasonic or Enermax PSU.