I posted a deal late last night on used original model N-Gage systems. I suspect it fell to page 2 before the (admittedly few) people who are interested in N-Gage saw it.
http://cheapassgamer.com/forum/viewtopic.php?t=46124
Basically, the price for used original N-Gage systems dropped to $50 (used to be $60) at Gamestop online and B&M (though sold out online, so use the zip code search to find one locally). It's a nice deal if you want an N-Gage without a plan, though you can always get GSM service for it from AT&T/Cingular or T-Mobile if you want (I got a 1 yr deal with AT&T to use with mine).
If you just want to use it as a game/MP3/Movie device (and not a phone), it does require a SIM card, but you can buy an unactivated SIM card off eBay for under $5 (including shipping) and that works fine. Some folks report that the used systems from Gamestop often come with an inactive SIM card included, though mine didn't.
I personally recommend the original model over the QD. Though Nokia fixed some of the superficial weaknesses of the original with the QD, they also stripped it of some of its best features (FM radio, MP3, stereo sound, USB interface to the computer, etc.). You can download an MP3 player for the QD, but the lack of stereo sound is a major disadvantage. And having to buy a bluetooth adapter or MMC card reader to exchange files with your PC is a pain when the original came with a far better USB interface, cable included.
Personally, I love my N-Gage. It's strengths FAR outweigh it's weaknesses, and it's weaknesses are mostly superficial anyway. It's the best phone you can buy, IMO.
-DM