You chose a 680 and 780 over comparable AMD cards that had more memory for less money. You were never going to buy the 390X under any circumstances. Unless you learned a valuable lesson from buying those, and only now is memory important.
Look at this guy. You don't know me and you're basing your post on my signature, why? But since you want to know my history:
GTX 680 cost $500 to HD 7970 $550 when it launched, GF wanted a GeForce - easy decision.
I actually had a HD 7970. Two of them to be exact. The horrible Microstutter made me abandon CFX. In a fit of insanity I sold my HD 7970's during the bitmine craze (good value in my opinion) and then figured I'd try out the "OMG ITS SO MUCH BETTER" SLI with two GTX 660 Ti's I had which totally sucked (GTX 970 Vram issues made me realize I wasn't crazy when I said I was having VRAM issues trying to load 2GBs on SLI GTX 660 Tis). Sold that and wanted to buy a R9 290 but that there Bitmine craze made them $600+, for a stock model none the less. So, I saw a used Lightning 780 for $420 at my local Microcenter and bought it.
My current solution is to sell of my Lightning, sell of the 680, and get the GF a 970 (her being hardcore NV) and wait for myself until R9 390X (I already said I got a budget of $700) and welp this rumor puts it out of my budget range.
So, want to try re-evaluating my buying habits? Or would you rather just take your foot out of your mouth?