Let me put it this way... workplaces... in general (when they don't employ me in IT or as an IT consultant) buy pre-built OEM systems. The OEM generally advertises the processor, ram, and storage like they're the only specs that matter
Last time I tore apart an OEM "work build i7" it had an i7-2700k (stock cooler) on a generic H61 mATX mobo (no VRMs), with 1x8GB DDR3-1066 RAM, no GPU, and a 1TB Toshiba HDD in a case I cut myself on 3 times trying to get the mobo out for testing... of course when you look it up all it says is i7, 8GB memory, 1TB storage... which from an outside "I know the basics about computers" perspective, looks good...
The guy had apparently looked up the system specs and saw he had a k model CPU... tried to overclock his computer because it was running slow.... annnnnd fried his motherboard and CPU...
Point being, the CPU doesn't control how fast a computer is... the sum of it's parts do... I've never seen a reason to go completely overkill on $200+ mobos, but a nice mobo with strong VRMs does get a much more efficient overclock... it took me forever to convince the owner that I should build any computer we buy, but after I did, he said fine... build ME one... let's see... So I was allowed half the budget he had been putting into his systems (cause I ran my mouth too much) and built him a $700 budget computer... I've been hand-building and upgrading my past builds to modern standards since then... (and he's since given me the regular budget for systems that require a workstation GPU)
There's a certain art to building a beast system that requires restraint to go with price/performance of parts... for instance... the 8320 has definite market niche, as it's the same processor as the 9590, it's just the D quality silicon that comes off the line... that means it won't get the 4.7 GHz overclock or likely not even a 4.5... but it'll easily hit the 4GHz mark an 8350 stocks at... when you pay for a 9590, you're getting the exact same chip as the 8320, it's just the A silicon... but as it's already been overclocked to pretty much it's max, you're basically just paying for AMD to overclock your chip with a guarantee it'll hit 4.7...
And TECHNICALLY... it isn't a true 8-core processor, it's got 4 Piledriver module which handle 2 threads and act as 2 individual CPU cores... but isn't as efficient in it's day as the old Phenom's which were actually separated cores...
A Devil's Canyon i7, per core, is ~58% faster... keep in mind a vast majority of programs don't use but 2 threads while doing "CPU intensive tasks"... now you have to get into SMT theory to understand hyperthreading... just to dumb it down completely... it has 4 cores that are working... it can handle 8 threads as it processes... whenever an active thread on the core becomes dormant, instead of waiting on the thread to become active again, it just processes the secondary thread in the meantime... there's also preloaded triggered threads and a lot of other things that SMT does to make the core more efficient...
Now, gaming doesn't really use hyperthreading... but...
https://www.youtube.com/watch?v=26UKz42uQ1Y
There's that... the i7 would purely be for video processing, virtualization, streaming, encoding, etc... things that actually USE 4 threads that you need done quickly...
IMHO, I'd buy one i7 and one i5... unless you're both running Linux and virtualizing Windows for gaming... or both streaming... the 9590 falls at a bad price point into Intel's performance territory... the 8320/50 are good buys for price/performance... but really at this price you could even consider dropping some computer bling and bringing in a 6-core socket 2011 which will murder everything from a processing standpoint (wouldn't improve gaming at all, but you never really said what you're doing with the PCs specifically)...
Back to the GPU talk... the 290 swamps a 770... a 780 will outperform a 290, and hang with the 290x (unless you're overclocking your GPU, and the high end 780's will overclock a lot better)... obviously the 780ti is the best GPU on the market, but a good 780 can overclock to ti performance as well... however, as far as price/performance... the 290 is DEFINITELY the best buy on the market for a high-end GPU...
I understand if you want to just buy what you originally intended... but if you ask the board to redesign something for $2500, you might find yourself getting some very good input as most of the people here are extremely knowledgeable in current hardware... GL with your builds...