Thanks everyone. I hooked up my computer today. I went with the Sigma 1606L because it was the least expensive one that still had cadence. I thought it would be useful for me to know what my rpms were because you're supposed to shoot for 80-90 rpms for a good cardio workout, right? It seems to work fine, my biggest problem was installing the components so they didn't hit each other! Getting them close enough wasn't a problem, but getting them far enough apart was.
Thanks again!