...with a shiny new GeForce 950 GTX...
It's quite possible that the rest of my system isn't fast enough to keep up with the new GPU.
Anyway, fitting it was the usual problem of trying to have multiple objects occupy the same physical space - in this case, the GPU, the SATA cables...
..and the hard disks, as the new card is somehow even longer than the old one (and that only barely fitted).
Yes, the letters "FTW" really do mean "For The Win".
There used to be a hard disk in the space on the right - I moved the SSD to there, and the hard disk to the blanked 3.5" bay. And then rediscovered that the reason I never put a hard disk there before is that bay is partially blocked by a metal tab and so one can't get all the screws in. I did actually consider drilling a new set of mounting holes, but that's too much hassle as I'd have to completely strip down the case. Perhaps another time.
The system did at least boot first time, which is good as unpicking everything and extracting the card would not have been fun. Well, it booted second time - the GPU needs an 8-pin power cable (not that it actually draws that much power), and refuses to boot with only a 6-pin one. It does however boot if you use a 2x6-to-8-pin adapter and connect the 6-pin cable to the lead that goes to the extra pins... GPU firmware 0, boggyb 1.
Unfortunately there was one casualty - my soldering job wasn't particularly good, and I pushed out the ground pin on the USB connector I bodged together for the front panel card reader (probably damaging the pad on the PCB as well). I may be able to bodge that even more by just jumping it across to a random bit of bare metal.