I like the parametric search, but searching a US retailer helps me focus on phones that are reasonable to source and use in the US. I could manage when GSM was two bands in the US, and usually two bands overseas and if you wanted a really neat phone you hoped it was quad band or at least tri band, because the really neat phones that were dual band were dual band on EU frequencies... now GSM Arena inevitably points me at phones intended for use in Japan and usually have a pretty poor match up with bands I'm likely to use while remaining flexible for use on other carriers in case it becomes a hand me down and the recipient isn't on the same carrier as me.

The GSMArena search does let you filter by bands, though I can imagine that getting tedious.