There aren't really very good 4x4 RTR solutions, I think. Buying a used racer wouldn't be a bad solution since you don't want to do the build yourself, though there's always the chance for duds... but you could ask around at the local track, someone might have something suitable for sale, and you could even try it out before buying, something you can't do with online purchases obviously... but buying from a well-rated seller on this site should be relatively safe and there's more to choose from.