.... Keeping in mind I am on a budget!
Unfortunately you picked the wrong hobby.
I have and indivision AGA V2 for the A4000. It works well but is a bit hard to configure correctly. (I find this is true with may of Jens' hardware, really amazing hardware but beta like software, but usable if you take the time. one exception the ACA have nice software as well.
The ACA is a really nice and fast card probably clock for clock the fastest 68030 out there (if the 030 is what you are after. you maybe after the 020 version)
The mediator allows for good flexibility , I have one again on my A4000, I would suggest the 3.3V version if you go this route for cheapest 9200 card and the most other pci card options.
As far as the vampire 1200, I would expect it to be awesome and well worth the money, but when?

You will have to ask yourself if it is better to have a bird in the hand or two in the bush.
Oh and nothing on your list was "cheap".