I've been with T-Mobile for over a year so my contract is up. For a little while Amazon was offering a t610 for -$170 but it looks like it's down to -$70 now (with a much higher up-front price.) That deal was also for new customers only.
I think I'll contact them and see what they'd charge me to upgrade to the t610 as an existing customer. If it's too much I'll investigate switching my number over to Sprint temporarily or something (I still have my old Sprint phone and I'd think I could activate it and switch my number over then cancel T-Mobile and sign up as a new customer and switch the number back.) I could also just cancel the service then start new service with a new number.