Well, I'll put it this way: I have a 5.5g iPod (Whiplash-modded and Rockboxed), and since I got my Solo, I haven't touched it. And I've only listened to my HM-801 a few times just to confirm that I prefer the Solo. I've had the Solo for about 3 weeks, so maybe I'm still biased by "new toy" euphoria, but I don't think so. I had the Classic for about 6 months before I heard the Solo, so I was pretty familiar with how it sounded.
As for the amp, I'd say go with whichever amp out of the top-tier portables you can get the best deal on (if you don't mind buying used), and whichever one whose presentation you think you would like based on descriptions. In addition to the ones you listed, I would consider the Pico Slim, TTVJ Slim, Stepdance, Protector, SR71b, and the iBasso amps. If you haven't already, check out the Headfonia portable amp review for one perspective and browse some of the Portable Amp threads here.
Edited by dj nellie - 5/2/11 at 1:16pm