I have a 1999 Atlantis (bought used), and a 1983 Stumpjumper and 1989 (I think) Miyata Terrarunner that I've tried to set up as Atlantis clones. Bottom bracket height is one difference; the Atlantis is lower than the MTBs. The Stumpjumper has a very slack headtube angle that makes it handle quite differently from the Riv (not as well, IMHO); the Miyata geometry is closer to the Atlantis. Both of the MTBs are heavier. For my money, neither of them has the combination of ride comfort and handling that the Atlantis has. But the Miyata isn't that far off. If I didn't have the Atlantis, the Miyata would be a perfectly acceptable substitute. Having said that, I'm not getting rid of the Riv.