CUDA GPU Simulators Finding the best one

Sorry if this has already been asked and answered… links to existing answers are very much appreciated.

We are looking at doing some simulation work involving GPUs. I checked out the download page for GPGPU-sim, but saw that it only supports CUDA SDK v3.1. Do you guys know of any better, more current (in terms of support, e.g., for CUDA SDK v4.0), etc. simulators, or is GPGPU-sim pretty much the standard (as I suspect)? We prefer free/open-source software, but any suggestions are welcome. Thanks!

Ocelot and Barra.