Get a GT 740, the GT 740 has a 128bit bus, the 730 is a little cheaper but runs at 64-bit bus. Here's one below that is the cheapest I've found.
I really suggest to never flash a VBIOS and to never OC a GPU. But putting that aside I would re-flash the VBIOS that came with it if you can find it and to possibly reinstalling windows.
If you can't flash it back see if you can put that VBIOS to stock values.