Welcome to Amiga.org :-)
I'd definitely go the 1200 or 4000 route, these are easier to expand and have the AGA chip-set which is bare minimum for alot of software.
If you can afford the 4000 you won't be disappointed! Simply add a zorro graphics card and enjoy beautiful high resolutions on your Amiga. If your feeling adventurous you could add a mediator PCI expansion board which will allow you to use voodoo graphics card and lots other cheap PCI peripherals. In the mean time check out Amikit the best emulation setup :-)
http://amikit.amiga.sk/http://www.elbox.com/
