Probably your best value route would be to find a used T2000, ride it enough to make sure all is well and then sell the T1000. Biggest difference in ride quality will be the carbon fork, which will likely be pricey and hard to find on it's own. Of course, while you are looking, it would be good to to test ride any other used tandems in your price range. I agree with others that a spare wheelset is very useful to have and a transferrable asset - but only if your new ride has the same rear axle spacing.