I bought all three of my Jems (555WH although not considered a true Jem by many people's standards, a 7DBK, 7VWH) and my UVMC off ebay.
The DBK and VWH were dead mint brand new, and I save myself about $1,000 by buying them from ebay. I got a free brand new case with each one.
the 555 was the only one I'm not completely happy with. The UVMC needed a good scrub-down and I had to patch up a small nick on the face under the trem... but other than that plays like a champ. Both were used, and it shows, but I still got good prices on them. It all depends on how much you're willing to gamble. Sometimes you get lucky, which I have, and sometimes you get something you won't be completely happy with, which has also been the case. Personally, I've been pleased moreso than dissapointed, no complaints here : )
Your best bet I think is to look for a VWH, and be willing to spend $1,400 on it. Rich might be able to help you out in that department... always hear good things about him.