^ With most 870 boards its x16/x4, but with that particular board it's at x8/x8 which is sufficient for most cards anyway, unless OP's going to use dual HD 5970s, which would then justify a FX board.
What's the difference between 'How much can you spend?' or 'What's your maximum budget?'? Doesn't the question 'How much can you spend?' expect an answer which is a numerical sum, say $200? And is it not the same for 'What's your maximum budget?'? You'd also expect the same answer, what differs? I really don't understand...
I just assumed the defaults on the 870 chipset and so recommended against that motherboard.. As for the 'how much' confusion, my point was directed towards OP to avoid asking for prices instead of providing a real budget figure..