I have an older SB750 and 790GX and the chipset itself seems to be okay. Needs a recent kernel though, well, today it's not so recent anymore.
But I don't really trust ASUS (I got some boards from the but still or better that's why...). There are some pros and some cons. But these VIA or sometimes also RTL chips that are solely made for one series of their boards, thus being proprietary chips, ... well. On the windows side you can't get generic drivers for them at RTL's site, you have to keep up with ASUS. And their website sucks, their driver mods suck (basically just rebranded drivers with some sh*t thrown in) and when they decide to cut it then you're lost.
Strange hiccups can happen on certain configs with their boards (I can sing a sad song of this.)
On the linux side devs probably have to beg through all instances for the specs to these "unique" chips.
I'd rather see that I'll get standard chips. Besides, VIA chips aren't really great stuff but then who am I to decide about sound chip quality with only some very good headphones. The VIA chips do the job but only when it comes to audio or network chips or maybe CPUs.
For the AMD chipsets: The integrated GPU becomes rather hot with these HD3300 ones, but then the power saving stuff is not fully implemented in the free driver yet so I will have to look at that later again. I once had a X1250 and that was rather cold. The display port stuff seems to be nice but I had problems with it and on Gigabyte boards you normally get the double amount of dedicated VRAM. Can't tell about how good it is working there though. But it is supposed to not use slower main RAM, not block main RAM and possibly the mem. ctrl. on the CPU could go to sleep more often if the main RAM isn't used for graphics. Correct me if I'm wrong.
So the AMD stuff should be fine though you'll better be off with fglrx at the start, you'll need a recent kernel and you should definitely avoid these obscure chips.
You can check with ALSA but in case something is wrong the chances of folks fixing the driver are lower than compared to some absolute standard chip that you can find in any forest or meadow.
edit: You should go for a socket AM3 if you buy a new one.