I have purchased quite a few plants (don't tell the fiance') from Andy's and I *LOVE* them. I haven't been disappointed in any of them.
Andy's is in a tie with my other favorite site:
Exotic Orchids of Maui.
Andy's has a larger ongoing selection but keep a eye on EOOM's site, they release new stock constantly. I've purchased beautiful vandas, bulbos, dendros (mini's), Dendrochilum, epi's, and Masdevallias from both of them and have never, never been disappointed.
They are a bit more pricey but worth it!
Oh, as mentioned, be very very careful with some of the e-bay sellers. As mentioned, "rare" is a very loose term on e-bay and can mean anything from a new cross, something harvested oversees (illegally), to "rarer than a dandelion"
Check it out carefully. There are a few sellers on there I really like but some I've come across are horrible!