[shaunsteig]

I'm trying to remember the sequence that I went through. I think I started with Clean Sweep Auctions, which is based out of Long Island. They deal with memorabilia (eg signed baseball) as well as cards, mostly low-to-mid level items (nothing in that ridiculous high-end that makes the cover of the bigger boys). I don't think that they required any references. I think my next step was Hunt Auctions; they might also not require any references. They also cover cards as well as memorabilia; I find their selection extensive and also will include some higher-quality cards (ie expensive enough to have fun browsing at but not to be able to bid on) as well as low-quality of high-interest items (such as your elusive 1952 Topps Mantle). Having won items from both of them, I think that was all I needed for references for the other auctions houses (Heritage, B&L, etc.), although I may have utilized the reference before completing a purchase.
Best of luck,
--S