I was on the verge of replacing my current video card (8800GTS 320) with a 9600GT for better compatability with DVB-T hardware acceleration in PowerCinema. However I've made the changes as suggested in the first post and have had quite an improvement in CPU usage. About half what it was. Not full HA by any stretch but still. CPU temp has eased a bit as well. C2D E4500 at 3.0 GHz.
TV 1 and 2 ~20%
TV 3 ~35%
C4 ~10%
That's acceptable for now but will still check out Media Portal and in time replace the video card.