Although I find the A900 finder to be wonderful and perhaps the standard for comparison, the electronic viewfinders of the smaller Sony models have been at least adequate in my use. I often use both the A900 and a NEX-7 or A55 within a few minutes of each other and don't have any problems switching between them. The current EVFs are much improved over that in the Sony R1 of a few years ago, and even that was generally OK. The extra information on display in the EVF is certainly handy. There are some minor annoyances as well, but as soon as you get past comparing the EVF with the A900 finder, you can quickly live with the EVF.
With regard to the OP's existing collection of good Minolta and Sony lenses, consider augmenting your tool-kit with a D800 and a choice lens or two. Although there are obvious disadvantages with respect to cost, bulk, and multiple sets of batteries, chargers, releases, etc., the convenience factor of semi-dedicated lens/body combos should not be overlooked.
Regards, Rick