that sounds really fishy to me. Video driver conflicts will absolutely give you a BSOD, like very few other software conflicts can. That your GPU just happened to up and die after upgrading to a new OS (and that's a really new OS, not technically beta, but in reality, beta for the marketplace) is too much of a coincidence for my spidey senses. I'd look at your graphics driver first. And gaming will definitely tax the driver. There are expected to be some driver conflicts with new OS's that just have to be sorted out. You might roll back to an earlier driver, or at least check that a newer one didn't get installed with the OS update to 10.
if it were me I'd even check the VBIOS but you might not be up for that. (You could possibly do an update on that --> but screwing that up can break a video card so you want to be a little careful.)
The obvious tack I would take is that your graphics driver is corrupted and you need to reinstall or rollback to an earlier version. Did you do a clean Win 7 x 64 bit install? That would be the safest bet, load minimal drivers and your game and see if it works. i've noticed already that the newest drivers that are out at the moment to support Win 10 compatibility have caused some problems with me in Windows 7 land until I have reinstalled older (more stable) drivers. It's just to be expected with the rollout of any new OS.
if your heart is set on a new video card then just do a little research. You can do really well online for that amount of money. the next questions of course are yes, power supply and can your system cool the card adequately. Personally, I'm a big fan of incredible deals on ebay, though they are a bit more risky.