Well, after installing my new HD4870 it seems I have encountered several problems... First of all, after a reset the board sometimes needs several attempts to start up. Fans spin up, then the comp shuts down, starts up again by itself, everything spin ups, shuts down... It repeats itself a few times then everything starts up correctly. Also my OC to 3.2GHz didn''t want to save itself in the BIOS. I managed to start everything up correctly at 3.2GHz in the end (trial and error on the settings in the BIOS's M.I.T.) and everything is running stable right now, no crashes or slowdowns. Though if I will need to reset the comp again (I hardly ever do that) I'm fairly sure the settings iwll reset yet again and the startup-shutdown loop will occur once again. Which is a pain, I'm sure. I just hope I won't need to reset it in the forseeable future.
As it stands now, I think I wouldn't recommend the Gigabyte board. Just get an ASUS on a P45 and you're set. Don't think I'll ever get a GA board again.