How to simulate low-end systems?

Although my game is relatively simple, I'm concerned about how it will perform on lower end systems. I'm currently doing a lot of stuff with mount points and schedules and I suspect it will eat CPU time like crazy.

I could enable the T2D profiler and find out where my game is spending most of it's time, but I don't think that will really help me. My entire game is run through script and I'm not enough of a programmer to know how to move bits of it into C++ to speed it up.

Using Alpha 2 and running in a 640x480 window I get about 300FPS on my P4 3.2HT with 2GB DDR2 RAM and a 7800GTX. Am I right in thinking that this is a hard limit in T2D and that the engine won't go faster than 300FPS? Not that I need it to go any faster, I just had something in the back of my mind telling me that I'd read about 300FPS being a limit.

I'm not particularly aiming at low end systems, but it would be a bit embarressing if my simple game requires a beast of a CPU to run properly.

I've spotted a few CPU slowdown programs on the net, but does anyone else have any suggestions for simulating how their games will run on lower end systems?