Hell yeah there's a difference!
Here's a comparison between my current TVS setup (blue), my old Katana setup (red) and a stock Elise (green). The 229whp Katana setup is just about spot-on with an S240 in power.
Notice that the increase in torque/power with the TVS vs. Katana is just about the same as the Katana over stock... so figure that getting a TVS setup would feel about the same as a S240 Exige over a stock Exige...
Enjoy!