I'd say hold out for an a3000, as it is basically an a2000 with most of the upgrades which really are required for practical usage. An inbuilt amber scandoubler/flickerfixer is a big bonus.
I probably wouldn't advise getting the a600 unless you are really in love with the form factor. Without an a630 it is next to useless.
a500 with hd8 is a nice cheap option - picked up one for $20 AUD the other day and it works quite well (the whole setup is quite bulky however).
An a1200/a500+hd8 combo will give you most of what you are after... but if you really have your heart set on an a2000 - try get a rev 6 board at least and get some confirmation about the state of the battery. Unexpanded, I'd say $80 at most (w/o monitor).
