Re: Champions or Hero System v5 ???
I was in a similar boat a while back, I used to play back in the BBB days, but hadn't since then (and lost the BBB). I purchased only the 5th rules, I haven't really missed the others, since I can fall back on all my old suppliments or work from scratch.
That is to say, 5ed was all i needed to get back into the game, I can't comment on the usefullness of the other suppliments. On a side note, i haven't seen it, but I have heard the sidekick is a condensed 5e 'book' and may be an alternative to get back in on the cheap. I don't know how much is missing from the 5ed book but I have heard its a good option for players (vs the GM).