A pretty basic computer\laptop can run NES & SNES Emulators. I was running 100% of NES ROMS & 99% of SNES ROMS smoothly and without any problems about 8 years ago on a crappy P3 600MHz Laptop with 64MB of RAM. Those are almost considered throw away computers now. You could probably find one for less than $50. If you ever get serious about getting into emulators let me know. I'm sure I can point you in the right direction to hundreds of hours of play time. Or you can continue your quest on finding a vintage NES Console...
-David