If your previous experience was with an A1200 then an A4000 would be a good choice. The A3000 is great, apart from the small range of accellerators (they have to be short to fit the case) - though if you can put up with that there's no better Amiga than the A3000 ;-)
If you're starting with a base machine then any Amiga will need serious upgrades to make it more than a basic hobby machine, of course you could always get a new A1 or Pegasos ... or make do with UAE until a primo machine comes up :-P
