If you like Tamiya, take a look at the DB01 Durga. It's belt, but the drivetrain is sealed like the Losi. It uses stick packs so you could easily run lipo, and uses the same wheels as the 501x. The owner of my LHS just built one with all the Tamiya hop-ups and it looks good. I think he said he was going to race it this weekend so I'll ask him what he thinks of it.
http://www.tamiyausa.com/product/ite...oduct-id=58395