I'll try to make a long story as short as I can. I'm using SS today as a result of the miserable experience I had with the HP ex485 MSS. Subsonic actually does what Twonky Media was supposed to do on the HP Media "Smart" Server.
The ex485 burned out 3 hard drives in less than a year. In my opinion, the form factor does not allow enough space around the hard drives to allow for adequate cooling. Since switching to an Antec 300 case I haven't lost any hardware.
I will never by another HP product. They are all marketing, low price, over-hyped features, and lousy quality.
A lot depends on your individual level of expertise when you're trying to figure out the best option for a Subsonic server. I often recommend a cheap refurb or starter DIY kit like are often advertised on Tiger Direct. You can ocassionally find Corei3 systems with 500gb - 1TB drives in a cabinet with room to grow for under $400, often reasonable foundation systems can be had for $199.
http://www.tigerdirect.com/applications ... t%2015-_-n
The other consideration is your budget. I spend way to much on my systems, but as I tell my wife, I don't drink or smoke - it's my vice.
I enjoy building from the ground up with the "Tim Allen" approach Har,har,har...
I currenly use Antec 300 cases and in my servers I now have Antec 380 Earth Watts power supplies. MY WHS build has an MSI 890FXA-GD70 mobo with a 65W AMD quad core 910e Deneb CPU with 8GB ram and 4 2TB drives.
I like using quad core low power consumption CPU's as my servers are on most of the day. My Server 2008 R2 box is on 24/7 running a 65W Xeon CPU with 8GB ram. That's what hosts my public server in the link below in a VM install of WHS 2011 in a 2GB VM. My WHS 2011 on the AMD box uses the Lights Out addin to put the server to sleep when no one is using the network.
You also need to understand that lower powered solutions may not do a very good job for video. If that's a priority, you need some power. What are your storage needs? 3TB drives are becoming affordable, if you only need to host SS for music, an itx Atom CPU with one big hard drive might just fill your needs.
There are thousands of "right" ways to go. The wrong ones you learn from experience. After every build, I realize what I should have done differently.
Good Luck