I would still suggest you to be looking at a proper TV set rather than NTSC games. You will loose on most of the Amiga software making it a very bad purchase!
Get a 1200 that switches to PAL and NTSC, expand it a little with memory and hard drive, and you have a killer WHDload machine that can let you enjoy most every game.
Hey, that is MY website
Maybe some of the US publisher games will run in NTSC mode, but I must stress on the futility of looking for NTSC versions of software when an A1200 can run in PAL just fine. You will miss on Uridium 2, Disposable Hero or Battle Squadron, three of the best shmups for the paltform.
An A500 cannot switch between PAL and NTSC so I would recommend against it.. I don\'t like A500s anyway, not even the Plus.
There's loads of US A1200 models, I had one for years and ran ALL PAL software I had...