I wouldn't be as concerned with the processor as I would the video/motherboard. I just built a HTPC using the an AMD 4450e and Gigabyte GA-MA78GM-SH2 board and it plays blu-ray flawlessly. It also only uses about 3% of the processor while doing it!
As long as you have a graphics chip that can hardware decode, than you don't need much for processor unless you also use the pc for ripping movies to a media drive.
I was also advised to get that mobo and by it's specs i guess i will.Did you get a graphics card as well,or are you using the one integrated with the chip.Does it support hardware decode as you mentioned?
Now I'm having trouble deciding the box as i want a small and portable one,and the power supply.I cant seem to find a decent 300-400 watt power supply.What did you decide for these factors?
If it was me, I would choose the dual core celeron, as it is basically a conroe core CPU, the same as the E2, E4 and E6 series. The only difference is that it has less cache memory and the front side bus is set lower too.
As hopefully we are all learning, direct comparisons between clock speeds are not a reliable indication of performance.