I'm looking at a set of manifolded steel HP 100s on craigslist. I'm not entirely sure the price is all that good, though. What would you pay for a set of doubles that need hydro and viz? What would be a "fair" price? I believe these tanks are ~$375 each new and they're listed at $280 with the manifold and bands but I've got to figure another $100 for hydro and viz, another $60 for O2 cleaning (don't get me started). At that price I'm at some $450 or so for two single tanks, if I don't have to buy new valves. Worth it?