Get the Tuniq, imo. I love mine, and it fits in my Antec 900 nicely. I had to mod my side panel 120mm to close it, but it was no big deal. It keep my G0 Q6600 at around 38c idle and 72c at 100% load on all cores (which will never happen in a gaming environment)
If you get the DS3 board, be aware that it has a considerable amount of VDroop. The Vcore you set in the BIOS won't be actual. My BIOS is at 1.537, my idle vcore in CPUZ is 1.504, and 1.424 under full load.
Supposedly the ASUS P5k has less vdroop problems, I wouldn't know for sure. Do some research.