First of all, since when was the Voodoo5 6000 in production?? it was a flop and was never even produced as far as i know...wouldn't mind getting my hands on one if one exists though.
Also, 4ns sdram is real expensive. Getting 64 megs of it on a video card is pretty pricey, let alone 128 megs of it...and until games start working in colo depths beyond 32 bit (like 40 or 48 bit), 64 megs is MORE than enough to handle all the textures. For high resolutions, it's the ram speed to worry about, not the ram amount.