HotHardware reviews MSI's SFF PC.  While not as stylish as some systems purely designed for HTPC use, there is a nice tradeoff, it's performance is on par with a M2N32-SLI.  Find out if this system strikes the balance you are looking for. 

If you are looking for a large HTPC case, that is still going to fit into a living room, check out Lee's review of the Thermaltake Mozart TS.

'MSI comes to mind as a company that initially approached the SFF market with some trepidation, but has since

found their stride, so to speak. MSI now has three different series of slim and small form factor PCs (Hetis,

mPC, and Crystal), each with distinctly different feature sets and target audiences.'

Here are some more Systems articles from around the web:

  
HTPC

• Hauppauge WinTV-HVR-950 @ I4U
• ASRock

  ALiveNF6G-DVI Micro-ATX Motherboard Review @ Virtual-Hideout

• Shuttle P2

  3700 XPC @ [H]ard|OCP

• Abit IL-90MV Core

  2 Duo Mobile Motherboard - HTPC Ready @ HotHardware

• Thermaltake Mozart SX (VC7001SNS) Slim Home Theatre PC Enclosure @ Futurelooks
• Antec Solo review @ DH
• Silverstone LC16M - The Ultimate

  HTPC case? @ OCModShop

• Thermaltake Mozart

  TX Home Entertainment Chassis Review @ Virtual-Hideout

• HDD Player Techsolo

  TMV 330 Review @ Technic3D