As per the support question.. I have only ever called 2 mobo manufacturers, but i have heard stories of all together four companies.
Soltek is the clear winner with support.. I emailed them with a problem once with a BIOS setting, got a very fast and very nice well written response, i was pleased.. i then emailed them back saying i loved their product and that i wished to get a case badge or some stickers or something if they had any, they don't yet carry them, but i was told that when they would send me an email requesting my mailing address and they would send me some stickers or whatever it may be.. Totally sweet. they are great people, and better yet, their motherboards are golden. I love my SL75DRV4 more every day. very fast and stable flawless operation, and i am into gaming too.. TWO THUMBS UP FOR SOLTEK.
As per the other that I called, was Aopen, they weren't very nice and didn't say much other than "NO" or "YES" or "MAYBE" was the guy's full dialogue.. they did not offer to help me fix the dead board i was calling about.. even though it was out of date (warranty wise) i was curious if i could get a replacement from them being as no stores carried the board any more and they said they couldn't help me.. that kinda peeved me... blah.
the other 2 i have heard of people calling and reporting on are Asus and MSI
both i was told suck butt.
for actual mobo recommendations I gotta give Soltek the nod.. the SL75DRV4 KT266A board goes for about $154 Cdn which is somewhere in the $90+ range USD, which i must say is fabulous deal IMO (comparing it to other mobos i have used).
on another note, there are so many good KT266A's out right now I take a leap here and say you would be hard pressed to find a mobo you would actually be disappointed with. (that is only KT266A - they seem to have a wealth of great boards with this chipset)
Good luck on your decision...