Important considerations, in no particular order:
#1 - If you do purchase the 9590, you should absolutely go with a minimum of a top end All In One Liquid Cooling System. This chip is set to 1.525V by default, and the top Air Coolers start to struggle to dissipate heat when above 1.4V when all 8 Cores are under 100% Load (most notably when calculations are being performed with the on die memory cache: Prime 95 Small FFT's, and Large In Place FFT's).
#2 - Very few Motherboards support the 9590: only three are listed by AMD, which includes the ASUS CH V Formula Z. Another poster on a different thread stated that ASUS has the 9590 listed as supported by the Sabretooth Rev 2.0. IIRC, the top Gigabyte and Asrock 990FX boards were the other two that AMD had mentioned. Then read the user reviews on Newegg and elsewhere: you will be looking for the most stable VRM's. I'm using the CH V Formula Z myself.
#3 - Choose your memory sticks carefully. Despite the motherboards mentioned in # 2 having listed support for higher speeds, AMD states that the 9590 will only support up to 1866MHz. Depending on the Motherboard and your particular CPU, sometimes higher speeds will limit you to only two sticks of RAM. I'm using 4 of the Crucial Ballistix Elite 8GB sticks (1866MHz) with no issues on the aforementioned CH V Formula Z.
#4 - Take the overclocking advice with a grain of salt: not every 8350 is capable of being overclocked to 5GHz, just because others have hit it. I was able to get a 10% OC (4.4 GHz) out of my 8350 before being limited by Cores 5 & 8. Purchasing the 9590 after the price dropped, and pairing it with a Corsair H80i cooler, granted me an instantaneous increase of 600MHz
Shopping for CPU's is a bit like buying a pack of trading cards: sometimes you get the run of the mill, and sometimes you get the pick of the litter
#5 - Buy a high quality Power Supply: at least 80 Plus Gold Certified with 2 separate 12V rails that have a high current rating. Anything less and you will be running into stability issues when using the 9590, let alone with either set up of the graphics cards you've been mentioning.
That's my two cents - good luck, and most of all, enjoy!