The bike is only part of it. Training is the most important thing. I race on a carbon £2k bike (which I admit, worries me sometimes). When I got the bike I was already race fit so I noticed the difference immediately. In 2,3,4 races you'll see all sorts from MAMILs cluttering up the bunch and generally out of their depth on 7k cervelos (always cervelos, for some reason) down to people looking pretty handy on old alu Treks. Train hard and the bike won't make a massive difference.
What does make a huge difference is wheels. Lighter, better rolling wheels are worht a lot more than a few grammes off the frame weight. Deep section will also make a huge difference. However, having seen a pair of the new carbon spoked Mavic cosmics taco-ed at a race the other day I see no need for a lowly 3rd cat as myself to risk that amount of money!