The CROSSHAIR V FORMULA-Z is the outright "best" board for the chip.... but there are other, decent 990FX boards.
The problem is:
Those boards are not cheap today (or when they were new, realistically) - they sell, USED for $200
You're investing in a quite dated architecture, considering the 9590 is essentially an overclocked 8350, which itself was an overclock 8320 (IIRC).
I hate to be the bearer of bad news, but the cost involved to get a compatible board is not going to be anywhere close to a proportionate for any "gains" vs the 8320 you started with.
You'd be better off returning the 9590 and sticking with the 8320.... Or trying to sell what you have and upgrade the entire platform.