if you like the geometry, then sticking with it is not a bad idea. riding fast is mostly about you. i good wheel / tire upgrade will take you a long way, and can move to whatever bike you have in the future. thats where i would start.

fwiw, on my local rides, i see a lot of "roadies", some faster than me, some slower. i have ridden with guys on anything from walmart mtb's to 12K cf road bikes, and like everyone will tell you, its the rider that determines just about everything.