Well I've been a body builder too in the past - albeit more strength training (specifically powerlifting). I never bothered with any of the supplement rubbish. I think maybe it helps (i.e. drugs, not 'supplements') if you're up to competition levels but I never got that far. For me, like the cycling is now, it was more of a test of myself, for myself than actively trying to beat anyone else.
The thing is that with most of these things, they're food and your digestive system breaks food down into fundamental stuff that get used to build new protein, fats, bone etc. So most supplements will fail by being digested. That's not going to be true of D-aspartate but from what I've seen from a quick google - it's all very tenuous 'evidence' for it boosting testosterone levels. *yawn*
