Check out Underground Racing's website. I think they list prices for their upgrades. Would you consider the Gallardo?
Edit: For Stage 1, it's $39,000 for both the Gallardo and R8. With 93 octane, you get 700 HP on both cars. With 117 octane, it's 850 WHP with the Gallardo and 1000 with the R8.
PSS10 Coilovers | TMS Camber Plates | LED Tail Lights | 219M Wheels | SuperSprint Race Exhaust | E60 Shift Lever | ZHP Steering Rack | GroupN Motor Mounts | RE Trans Mounts | AKG 90A Subframe Bushings | AKG 95A Diff Bushings | AKG 90A RTABs | TMS Subframe Reinforcement Plates Epoxied | Driver Schroth Quick Fit Pro | Passenger Schroth Quick Fit | PFC 08 Pads Front | PFC 06 Pads Rear | CPI Stepped Headers | Motul RBF600 |