"The Amiga" will always have a special place in my heart. Yes, its not the fastest, yes its not the most expandable, but, damn is it ever pretty to look at and use! (For those that don't know, the Amiga 1000 was "The Amiga").
The closest analogy I can come up with is:
It was the first release of a multi-sequel movie where each sequel was either pretty good, or an outright fail, but, it left you always going back to watch the original.
I think the A1200 is the "best bang for the buck" in terms of power and expandability.
I think the A3000 is the best looking of all the powerful Amigas.
I think the A4000 is the top dog if you just want to build the most expandable, most powerful Amiga.
So, what do you do in this situation; pick the one that suits you best, or, get 1 of each and enjoy!