I think that the question needs to be refined somewhat... Ultimate 1200 for what purposes? For example if you're going to only be doing vintage type computing, do you really NEED a USB adapter?
Also, I'm not sure what the specs are on the BVision... but if you have a dedicated graphics "card" in there, why would you need a scan doubler/flicker fixer?
Depending on what you plan to do with the machine, "ultimate configuration" is going to have different requirements, unless all you're going for is some kind of "My Amiga has every add on ever made, that proves I have a giant penis" thing rather than trying to build a computer where you're actually going to use all the things you put in it. You may end up spending a lot of money on something that has no real use, when that same money could be put into an enhancement that would serve your needs better.