I'd recommend getting a good (read: as deep/big as practical/possible) for any lens you end up with. Arguably will make as much of a difference as changing lenses.

If you mostly shoot stopped down, look at the Industars, some folks say they are sharper than the Jupiters and go for even cheaper, plus they have aperture click stops. 52/53mm f/2.8, the L/D version has lanthanum glass for even better performance. I had a regular I-61 on my first RF, a Fed 3b and the J-8 I have now does nothing better except f/2.0.