i haven't really found one, so i've been using pure data to push my system load with cakewalk by sending loads of midi data into it and manipulatin automation fx and mixer components for audio data. i have a vid of an experiment here:
kontakt madness one thing i've tried is take an audio track, turn on all the prochannel modules, !reduce the gain and volume on all the tracks! clone it ten times then drag a different loop into each track and copy special about 300 iterations of them. clone those ten tracks ten times, select all the audio and select bounce to clips (this will be the first benchmark). when that's done check your audio folder and there should be a couple of gigs of audio tracks in it. then, while the project is playing back, ctrl+click and adjust any module control in the prochannel to set up a quick group and change the parameter for all 100 audio tracks (like low pass cutoff in the pc eq) and see how the cpu responds. write-enable all automation and do this for several modules and parameters until your system shows signs of stress. the next layer i did is set up in this module 16 tracks armed for recording (2 tracks for each for my audio inputs) and record anything (or nothing) into them. what you're probably going to see at this point is the hard disk icon clipping red. this will help you tune your io buffers if you're going to be doing lots of recording.
those are the basic ones i do. hth.