The S2000, my former car, made 120hp per liter NA stock and 135 per liter with bolt-ons(at the crank) I had it running mid 13's with bolt ons but it's nothing compared to a Z06 or modded crossfire when it comes to straightline. Boost it and it's another story, but all that power in a light car prone to oversteer can be dangerous.
Zo6 or a boosted S2000 would be my replacement if I lost the SRT-6 and couldn't find another. The ZR1 is a bit out of my price range but a beast non the less, if you can get all that power to the ground.