GTXJackBauer
Your CPU WILL bottleneck.  I have a X58 that had some bottlenecking issues with my 780s and that was a few generations back.  I would highly recommend on upgrading your PC system over the GPU and just wait till one of them affordable 2060s or less come outs at a later date for 1080p which should be more than enough.

Cool GTX
My X58 (MSI Big Bang) with i7-950 @ 4.1  -- would handle only 0ne 10 series GPU, may be a CMOS thing, it choked on two EVGA 1080 

I hand no issues with two EVGA 980 SC though
 
My MB was limited to PCIe 2.0 also....
 
I'd look for a deal on a Z97 to take advantage of Newer GPU on a budget (still uses the cheaper DDR3 RAM) (Win 7 friendly) 

GTXJackBauer
Your CPU WILL bottleneck.  I have a X58 that had some bottlenecking issues with my 780s and that was a few generations back.  I would highly recommend on upgrading your PC system over the GPU and just wait till one of them affordable 2060s or less come outs at a later date for 1080p which should be more than enough.

TheParagonHero
X58 was giving me a bottleneck with a 970, before I had moved on to Z97 with the Haswell refresh. Honestly, it's been--luckily--much longer lasting than X58 was.
Honestly, where you are now, I'd wait until the chipset that supports DDR5. That's what I am doing. It's close.
 
But if you can't wait, drop at least $300 on the CPU so it lasts.

vengeancewithin
Hard to argue with free. I have a X58 SLI3 up and running in another room and it ran games about as good as well as my X99 does with a GTX-980. Mine has a X5670 Xeon in it so I can confirm the board will run XEON CPU's. Maybe it was bottlenecking and I'm just to daft to notice.
 
Still if it's free I don't see the harm in trying it. Not sure about that PSU though nvidia recommends a 650w PSU for the 2080 and say they have a TDP of 215w not overclocked.  The X58 CPU's have a TDP of 130w for the i7's and 95w for the Xeon models if memory serves. If the PSU is 430w that doesn't leave a lot room for overclocking and other components. Personally I'd say try it and get a PSU that'll go into your next build. I wouldn't spend any money on upgrading the X58 though. 
 
If you do decide to fiddle with the X58 I have a i7 950 you can have if you're in the lower 48 states. It has a higher base clock than the 920. 

arestavo
Well, the lower the resolution the more your CPU will be the bottleneck. I was bottlenecked with two 980 Tis and a 4930K and a 5820K at 1080P, but not a single 980 Ti.
 
Now at 4K even my SLI 1080 Tis aren't bottlenecked at 4K for the new games that I play - although some games just get eaten up even at 4K (140+ FPS, like Sniper Elite 4 in DX12 mode).
 
You can always use Nvidia DSR to increase the resolution should you not be wanting to get a new monitor. It's basically like supersampling the game, and then it gets downsampled to your native resolution. https://www.geforce.com/hardware/technology/dsr/technology 
 
 

Cool GTX

HeavyHemi
I'll be the first to point out he's only got 6GB memory. That's not going to cut it with modern games. He's going to be thrashing the drives which would defeat the purpose of any upgrades.

6GB ?
 
Signature says 32GB RAM
 
Maybe I am missing something ?

markiller
I recently upgraded my X58 from a i7 950 @ 3.4Ghz 4C8T to a X5675 @ 4.2Ghz 6C12T (Will go to 4.4 but not 100% stable in everything).
 
I doubled my quad and multicore performance and it is ~30% faster single core, and best of all it was just 45 bucks on ebay. Based on synthetic benchmarks its about 80-85% of the performance of a stock 8600K and close to a i7 4th gen in performance. Since its a 95W chip it also runs relatively cool. In game FPS gains were typical under 10% since at 4K and 1680x1050x3 nvidia surround I'm already GPU limited. An 8700K would probably only get me around an extra 2-5FPS at those high resolutions. I Can't recommend this upgrade enough.

warcobra
So I don't have any pictures right now but I have tested a 2080 in my X58 system. It was a EVGA x58 Classified 3 with a W3680 at 4.4ghz. So I also tested it in comparison to my x99 system and the fps in most games that were cpu driven was anywhere between 3-11 fps. So 11 fps sounds like a lot but the only time you would see 11 fps difference is when the game was running upwards of 100 fps. Also If you play at a 2k + resolution than you would have less of an issue with the cpu being a few generations old. So if you wanted to pick up a 2080 (Non-TI) I would put that extra money away for a new motherboard and cpu and ram for 2 quarter next year. Ram prices will be dropping a lot and newer architecture should have a little more time to drop in price and mature. At least that's my look on it. Good luck choosing.