Same here. I really wanted to have one bike do it all. And after having owned the TE250 for several years I thought that the 450 or 510 might just fit the bill. I rode both and figured out very quickly that I really needed (wanted) two bikes. One for trail rides and one for dual sport/ADV rides. The 450 is a great bike. However, the close ratio tranny and lack of counter balancer are the limiting factors. Even geared 15/48 (stock for my 250 is 13/50) you run out of gears very quickly. The 250/450/510 are great trail/race bikes, and I've done several 200 mile days on the 250. My 610 is so much better for longer more casual rides. Having a smooth power band and a wide ratio gearbox makes the ride so much more enjoyable. Good luck with whatever you decide.
09' TE-610, 06' TE-250