the HDD is 320GB, unless im looking at something else. that doesnt seem that big for a HTPC to me knowing how quickly i fill up the sky HDD
*edit*
found a 500GB one, but thats not amazing for a HTPC
Define amazing?
It's ultra quiet. I cannot hear it when sitting 2 feet away from it. It offloads all the rendering onto the GPU to avoid the need for an expensive processor.
It has gigabit lan installed for streaming 1080P content across a network, which it does wondefully.
It also has optical out for connecting to a home theatre amp, which it also does perfectly.
It runs Windows 7 very well, extremely responsive.
It's tiny, and can be attached to the back of the TV's wall mount points to keep it hidden.
Built in wireless N to stream movies across network and other data
A tonne of USB ports.
Did I mention it's a similar size to the Wii and much lighter.
If you want more storage, get an external HDD and plug it in. This is a lot cheaper than faffing around with silly home builds. It's a lot smaller than you could build yourself, quieter and cheaper.
I've used mine daily for the last year near enough and I have it streaming 1080P content flawlessly. Not to mention it can multi task... HD movie plus web browsing on separate monitor. It has HDMI & VGA out. Supporting dual monitors.
The downside:
It's an Acer... but for less than 200 quid £320 if you add a 1TB NAS drive to the basket to stream all your HD movies. Well that's a pretty good bargain if you ask me.
However... feel free to custom build a server/home PC inside one of those ridiculously large Opera cases that have fake drive bay covers and come with a cheapo PSU. It will be the same size as your telly. I've had one and put it in the bin!
P.S. You cannot compare Sky HD to content on a PC. PC's use many different file formats and containers and treat them very differently to a sky box. 100 movies on a sky box wont be the same size as 100 movies on a PC.