I think it's a great idea to get some new biking clothes that fit you- clothes that fit make you feel good and look better. I just got some new screaming yellow and neon green bike tops because my old ones from 4 yrs ago are just too tight. It feels great having the clothes I love feel comfortable again (in a larger size) and not stretch over my 'extra padding' areas.

But getting a new bike?...I just don't think that will make you ride more except maybe for a couple of weeks when the new purchase is exciting. Assuming you already have a bike that fits you and you can ride. How is sitting in your living room working on bike parts going to make you more fit or slimmer? To me, getting a new bike and fussing with all the do-dads that you are going to need to get to make it work for you simply puts off the moment when you actually are going to sit your butt on a bike and ride. Why now ride one of your bikes tomorrow instead of shopping for new bikes?

My 2 cent advice... Get the new clothes that will fit and feel better, no matter what size it takes. Then sit your bottom on the most comfortable bike you already have and ride around the block a few times in your nice new screaming yellow duds and enjoy the wind in your hair. Get home, and have a big glass of ice water and congratulate yourself.