Well, I know for damn sure you don't want my input ;)
.....seeing how I already jumped ship.
BUT - the e34, particularly these 535iM's, are fabulous cars, plain and simple. They also can turn the corner and become more maintenance than they are worth. Yours does not seem to be at that point, but it's a point that's out there, lurking. That's the unfortunate reality when age, mechanical systems and budgetary concerns collide. At what point does it cease to make sense?
Anyhow - there are some fun vehicles out there, and not too distant from your 535. Bill's note about a later model e34 525 should ring true. Great cars are out there, the initial cost may be a bit higher, but the maintenance should decline for a while. Of course, the more you pay up front, the less you pay for maintenance. Or at least that's how the math is SUPPOSED to work....
As noted - bring it back to almost-stock, at least as far as looks, and get some money for the parts. Your car has been modified simply and tastefully, and that's a plus. Nevertheless, while you may get some money for the wheels on the car, there are few who would increase the purchase price for the underhood visuals you've done, nice as they are. Swap someone for stock parts, bolt them on, and get some cash in the process.
Whatever you do, don't travel the road I have gone down. It's like crack cocaine - far too addictive
--Micah O'C
'17 M2 6MT, Mineral Grey
'04 330i ZHP
'88 M5 2791445
'92 M5T BL01001
formerly '90 535iM, '92 525iT