Manual 540i. V8, rear wheel drive. What more could you want?
I would have gone with the M3, but the E36 M3's are crap.
Audi seems like a good choice, but unless you need AWD, it isn't worth the extra cost or weight. That and after riding in one, I wasn't that impressed with their interiors. I know many thing their interiors are the best in the industry, but it wasn't that great.
As for the '97 A8, might be a good choice if you can afford the repairs. I imagine since this car is rarer than other Audi's that the cost to get it fixed might be considerably higher.
528i... not enough power.
In Russia, choices choose you!