asrock bios does have some issues that manifest mostly in the bios freezing, but to be honest, they all have a bug or two that are usually fixed with a bios update. the audio codec is the same on the extreme 4 and G45 so I can't imagine there will bbe much of a difference there. the stock cooler will keep it from overheating (hopefully) but I do recommend buying an aftermarket cooler.
They're terrible value for money. That's the opposite to what OP needs considering his budget.