TL/DR: What is the cheapest GPU that can drive 3440x1440 @60Hz? What is the most powerful GPU I can power with 2x 6 pin power connectors?
Full version: I have a ViDock 4+ that I plan to use to connect a new monitor to my laptop. I think I'm going to go for 21:9 3440x1440 screen if possible. I want to get either the cheapest GPU capable of outputing 2d to this screen @60Hz+, or the most powerful one I can manage to stick into the ViDock, so that I can run some games with my rig too. The final decision will depend on how much of a compromise in performance the best GPU will be, for example if I can't get at least 1070 to work with the ViDock, it is probably not worth it to buy an expensive GPU at all since the performance at native resolution will be lack-luster anyways — I can game elsewhere and just use this for work. If I can get something powerful, great!
ViDock 4+ is effectively an adapter from PCIE to ExpressCard, so it enables you to connect an external GPU to a laptop with ExpressCard slot. It is limited to PCIE 1x but in practice this matters a lot less than you might think, it's like <10% fps penalty in most games compared to 16x. The 4+ is an older top-of-the-line model that comes with 2 power adapters, one labelled 150W and one 75W, both extremelly cheap chinese trash. They produce waaay too much noize and I would like to replace them if possible (any suggestions here?). 4+ has 3 input power sockets on the outside, 2 from the main PSU, and one from the smaller one. There are 2 power cables going off of the board and both end with 6-pin plugs. ViDock also sells something called «6+2 Pin PCIe Aux Power Cable» that they claim can «upgrade» 4+ to support 6+8 cards, but they recommend to «not go higher than GTX 760» after the «upgrade». I can't order this cable, their shop is down for the last couple of months. Maybe I can use some kind of adapter instead? Maybe I can use a normal external PSU to power the GPU?
If you can suggest a better eGPU solutions, I'm open to that as well.
So, with this information, what is the best GPU to get, and how do I power it?
(Somewhat) irrelevant additional background: I'm running my trusted thinkpad x230 and I'm now in a position where I want to upgrade my monitor. I really want extreme ppi and ultrawide, something like 34" 21:9 5040x2160 but this doesn't exist yet. I can't find any 16:9/16:10 4k monitors with ≤24" either. Anyway, my x230 (HD4000) is limited to 2560x1600 @60Hz via miniDP or 2x 4k @30Hz through the official dock (which I have too, not vidock). 30Hz is not good enough for me, so I'm looking or other options. I don't want to upgrade the laptop because there's nothing quite like it on the market for my needs, and I don't want to maintain a second machine as a desktop. So my options are 25" 4k screen or an 3440x1440 21:9, and I would need to connect them through the ViDock or other similar solution. I have run an older ATI card with the ViDock a couple of years back and I was even able to pci-passthrough it into a Windows VM, so I'm quite happy with this solution, I just need to find the GPU that would suite my needs.
Thank you in advance folks!