Still having troubles with the blaqbox eh?
it can be hard trying to find the right hardware when alot of the tested hardware is superseded, and I'm not really going to be much help here, however...
I ended up using an ASUS P5K Pro (full ATX 775 chipset). It is a Crossfire MOBO so that part of it is kinda wasted, however the onboard sound works well and have had no other problems.
I expect though you're after a MOBO with integrated HDMI our onboard video? Not sure about this. I tried the Asus P5E-VM HDMI motherboard at one point, thinking the G35 onboard video would work - however it turns out that although linux drivers are around for the X3100, the latest X3500 integrated video doesn't currently work (or at least not for me).
Might be easier just to get a separate video card and and decent MOBO with supported audio...?
Sorry I'm not much help.