Instead of 6000 random ROMs, use a to download a "MAME 0.260 ROMs (split set)." A split set includes the parent ROM and clones separately, but you can use a clrmamepro filter to keep only "Working" and "Parent" ROMs—which will yield exactly 7,000–8,000 playable games.
To the uninitiated, the name sounds like a mouthful. Let’s break it down: download work mame plus 6000 roms extras deluxe