I have never heard of the OSP DD-502 (Yamaha and especially Roland are the big names in e-drumming) but did a quick search and it seems reasonable for someone, like yourself, that isn't sure how far they would take learning drums. I agree with Adrian though, hit a local store (especially if they happen to sell a model that you are looking at) and give them a try. You don't have to be a pro-drummer to bang on the drums in the store, so don't worry about what others think. Tell them that you are looking for a low cost electronic drum set to see if you want to pursue drumming...
WARNING: DO NOT CONNECT ANY ELECTRONIC DRUM SET TO YOUR RECEIVER/AMP AND THEN TO YOUR AXIOMS! THIS IS BAD AND COULD CAUSE DAMAGE TO THE SPEAKERS! Alan chimed in to my question about it a couple of years ago and had a more technical explanation, but just don't do it. Instead, get some nice 'over-the-ear' type headphones and jam away! Don't use ear-bud style or small headphones as they are greatly lacking in the lower frequencies. Then, if you like what you are doing, buy a dedicated drum amp that can grow with you.
