Well, I've finally finished my mATX build, so I guess I'm ready to join the club?
Custom modded/painted SG03 w/ 2 CM Red R4 fans
Xigmatek 700w Non-modular PSU
16gb (4x4gb) G Skill Ripjaw PC1333
Intel i5 2500k
2 ASUS 6870s in CFX
ASUS Xonar Dx
WD 500gb SATAIII HDD
Crucial C300 64gb SATAIII SSD
I'll be honest, I did not need all the power in this setup. However, I was sick of enthusiast PC users and builders telling people that they "can't build anything powerful in anything smaller than a full tower." To that I say, look at what I've just done. Crossfire, water cooling, AND with a non-modular PSU. This isn't to say that I won't be using this rig to it's full potential though. This machine will be at LAN parties with me almost every weekend this summer.
Anyway, on to the good part, pictures (bad quality)!
As you can see I've painted the mesh and insides red. You cant see the motherboard as it's covered in a PSU and wires, obviously. You can (sortof) see the H60 radiator near the front, and the tubes too if you look carefully. I also cut a 5th expansion slot in the case to allow for the GPUs and sound card. The top PCI slot where a crossblow style fan is usually installed currently has a fan controller for the 2 front fans.
At stock, the GPUs idle at 35c, and the CPU idles at 28c.