I'm gonna say, Volvo 850 T5, can spend £2k on a half decent one then another £1k tuning it and you'll have 300bhp that'll be very reliable and be quite quick aswell. Only problem they look a bit boring.

Vectra SRi?
Golf VR6?
Audi A3 1.8t?
Puma 1.7? - As girly as they look everytime i drive one i can't help thinking what a bloody good car they are and for the 2-3k they fetch these days a bit of a bargin really.