How rough are you planning to ride? If you plan on doing any hucking and jumping, I would suggest the 3500. The navigator 50 would be up to a little rough riding, but neither bike has bouble walled rims. If you are not that interested in speed, the 3500 with slicks would do well in your price range. Test ride the bikes to see how well they feel to you. Ride some other brands just for a comparison.
[OK, scratch the Nav 50. My bike dealer is telling me that it could take 4-12 months for me to get one]
What part of Illinios do you live in? There is three Trek dealers within 50 miles of my town. It should not take that long to get a bike even if it is a 2006.