This thread should be in the "New System Build" forum of the Hardware section.
But let's see. The CPU and RAM are fine for an HTPC; you should actually consider getting a discrete graphics card.
Read this. Nice little article about HTPC graphics cards.
What is your budget, btw? If you can afford it, an Athlon II X4 620 would be a worthwhile investment too. Extra cores are better than higher clocks in an HTPC.
Otherwise it looks good.
My setup has been running pretty much nonstop for 2 years.
Stuff I bought new
Shuttle skt478 box, I don't even remember the model, it just works
WD 160gb sata drive
Craigslist scores all under $40
1gig mushkin ram
Win XP pro
HP branded Radeon x300
pioneer bluray 203 drive
logitech dinovo keyboard
random logitech wireless mouse
I don't store tons of content on the box
Youtube, hulu, itunes, my usb key, pandora, last fm, and netflix on my xbox provide most of it......the pile of dvd's/bluray disc do the rest.
A logitech xbox edition universal remote helps but the keyboard and holding ctrl to zoom text does most of it.
I've made $11k selling random crap on ebay and craigslist on it.
I built a 68 camaro using it.
It's fed via ethernet cable, it only has 4 usb's
optical from onbd sound to an onkyo receiver, dunno the model, was $1200 and top of line 2 years ago
DVI from Shuttle to Mitsubishi 65" DLP, also don't know model, but it's huge and given me zero probs
Polk audio HT speakers, 6.5" midsize in front, center chan same size, satellite rears, 12" powered polk sub.
Made the mistake of buying monster cable, but it works.
HMDI out from receiver to mitsu 65"
HDMI in from xbox
I've got 1 spare HDMI in from cancelling Dish network, I don't miss it.
If i need to watch anything I can't see online, then that's what bars and girlfriends are for.
Simple, cheap, reliable.
It makes me not forget the point was great sound came from the receiver and speakers, the TV is massive, and for light use computing being under the accepted standards is fine if most of what I do from the couch is using MS office, mild photo/video for my ads, and web use.
I thought about going with a new setup, but then I cranked up Modern Warfare 2 after watching It Might Get Loud and forgot about hdmi 1.3a, 240 refresh rates, and really loud quality 5.1 beats weak 7.1 speakers systems and cheap receivers.