Hmm... I'd say, go for the cheaper alternative. If a fully tricked out A1200 with graphics accelerator, PPC cpu Accelerator, Soundboard accelerator ( is there such a thing?), USB-stack, Internet-adaptor, and all that stuff is really cheaper, then get that.
I think just a stock A1200 with some better HD and more Ram is cooler and more true to what an A1200 was meant to be tho.
Believing that, and aiming for, an Amiga that is equally supreme against current IBM-compatible PC technology as the original A1000 and A500 was, is an utterly unfeasible dream.
Not unless you actually want people to afford the damn thing.
Lots have changed since the 80's, and the fact that the PC is a cutting-edge platform, that moves at a breakneck speed compared to all of it's competitors ( Sony, Nintendo, Microsoft themselves(!)) is one of them.
I think I have a pretty good shot at seeing this with some perspective, since I'm not Amiga-exclusive like so many others on here, and I'm too young to be interested in the Amiga from a purely nostalgic perspective.
What I think really set the Amiga apart, was that it was a fusion of game-console and PC mentality. A nice sort of medium between the two. Using custom chips and esotheric processors coupled with an OS specially attuned to the hardware, allowing you to do more things than play games with it, was the general brilliant idea.
If you wanted it to be a console it was a console. Just load the game straight off the box. If you wanted it to be a Personal Computer, it was a Personal Computer. Boot sequence and all.
Trying to one-up the PC is not a feasible idea, and IMHO, it hasn't been for a long, long time. Even Apple, that still exists, lost that battle. They're actually using PC-processors nowadays, you can run friggin' Windows on a MaC!
That's a failure.
No, I believe a new Amiga should be made with the original mentality, which was that it was a cheap PC that did the job, but was also a great game-console. Being cheaper than the competitors is out of the picture, since the change in manufacturing and capacity, with all of the different manufacturers of PC hardware there is now, has made the basic components as cheap as they can feasibly be. Being AS CHEAP as the competitors, to some degree, might be a feasible goal tho.
Alas, it then boils down the ULTIMATE core of the Amiga, IMO: The fusion between PC and Games-Console.
There's nobody to my knowledge who's doing this right now, and doing it well. NOBODY.
That's the goal, that's the golden egg. Keep the eye on that ball... And you're gonna' hit a home-run.