What parts did you use? I built my main rig a few months ago with almost top of line components but I'm not sure what is needed for a htpc. My main use like I said is for streaming media, and surfing the web probably
I used the following -
Asus P7H55D-M EVO microATX motherboard
Core i3 530
4gigs of g.skill ddr3
Intel X25-v 40gig SSD (already had this that I got from work)
Hec HTPC case (7k series)
Seasonic TFX PSU 300w (to replace the cheapo hec PSU that came in the case)
LG Blu-Ray/HD-DVD combo drive (I already had this)
1Tb WD AV-GP hard drive
Logitech DiNovo Mini keyboard/trackpad combo
Windows 7 Pro
I went with the i3 530 since it is more than powerful enough, has a decent built-in GPU, and runs relatively cool and doesn't draw too much power. Works great using HDMI to my TV, the newest drivers will compensate for overscan, and handles anything HD just fine.
The included power supply that came with the case was so cheap I opted to replace it from the beginning with a seasonic TFX power supply, that had very good reviews.
So far this system handles everything I throw at it. I stream most of the content from my NAS server that stores all of my videos, and the large hard drive is mostly for downloading stuff onto the machine so as not to use the SSD for much storage. I already had gotten that SSD from work, so it wasnt really needed for a build like this but I figured I would throw it in there anyways.
I was torn on getting the logitech dinovo edge over the mini, but the tiny keyboard/trackpad combo works wonderfully on this system for media center and basic use. I am not typing up anything on this machine, so the tiny keyboard is just fine.
Here are the pics to show the size of everything -
The keyboard -