If you paid $650 for a 20GB, consider yourself lucky. I won't even tell you how much luckier than you I am.
A friend of mine was on a waiting list for these things before the tuners were even ready for the Mark IIs. He paid a whole lot more than you or I for the 2 he bought, and he's so busy he still hasn't had a chance to install them.
As for the Dension or the Neo - I came very close to getting a Neo, just before the final price drop on SONICblue's site. And I'm glad I have an empeg. With all the learning I have been doing about car stereo setups and other things, I realized that have a 3.5" based model is just not worth it. Especially in my case.
I drive a Honda Civic in an area with rather badly maintained roads. My CD player skips all the time. I can't wait to have my empeg installed. And just for the helluvit, I'm getting a good portable CD player for it's AUX, in case I have a CD I want to listen to that I haven't ripped and encoded yet.