The 990FX boards are high performance unobtanium so first of all, good job getting access to one. You're probably all set.
FX-9000 is not AM3 but
AM3+ which doesn't sound like a difference until you have access to the boards that support it.
The FX-9590 is the premiere space heater that needs the type of water cooling I built for the FX-8370, now on a R5 3600.
If the Vengeance kit is too slow, some Ballistix Tactical or G.Skill Sniper kits are an outstanding combo but good luck finding them.
The OC options of the CPU and board should be agreeable for
F3-2400C11 and similar. I chose a
F3-2133C10 kit which also works great.
The challenge will be almost entirely related to keeping the 990FX chipset in check. At 1080p144 desktop or 2K90 VR expect runaway temps.
I paired the 8370 to a few 970 boards and 4.5-4.6GHz seems to be the upper clockspeed limit and there's a difference between boards.
It's faster than a stock 9590 but that means almost nothing between 4-5GHz.
I don't have experience with any GTX900 setup but it's already behind my RX580 and that's bad.
If SLI is the goal, a pair of 1080Ti cards might be more suited but I haven't seen any of those in forever.
For any mainstream desktop or VR gaming it should be pretty close to ideal. It's pretty exciting. Good luck.