It depends on how much experience you have. If you can fly a very fast and highly manouverable plane, try the Sickle (Grim's underground lab). The 42" version with a Norvell .25 and a mousse can will fly around 110 - 120 MPH.
I build them for about $3.50 ea and construction time is about 1.5 hours. I've built 6 in 9 hours including radio and engine instalation.