First off, congrats on your training and commitment. I wish I had the time and I will live vicariously through you and you accomplishments. You have a great opportunity to learn from other racers and pick up on what matters. You could go out and buy a $12,000 Pinarello, but if the bike doesn't fit you are not going to be productive. Obviously all the weight weenies will tell you wheels, tires, yeah, they make a difference, but it's still the engine. I'm sure in the racing arena, you will be surrounded by dream bikes, it's all about the dollar bill. It also sounds like if you are outgrowing your bike, your fit is what may need to be adjusted. My advice as recreational rider with friends doing Ironmans, keep you bike and ride the piss out of it. Lighter tires, yeah thats a start.
Take a look at the new Bicycling 2010 buyers guide. Your timing is perfect and the economy being what it is, there are more mid-range great carbon, ultegra bikes cheaper than ever. Start looking, do your homework. I've seen folks on hugely expensive bikes and they can't ride, and I am more impressed with the dude or girl that hoofs on an older steed!