I've owned an F, F2, and F3, and I've played with an FM2, the F is the only one I've kept. The F3 was nice I bought it in mint condition with a 50mm 1.4 and SB-16 speedlight and used it for several months last winter. I eventually decided I'd rather have something all mechanical, the F3 is now on permanent loan to a friend. I bought an F2 Photomic with 24mm 2.8, 50mm 1.4, and 135mm 3.5 non ai lenses a short time later. All in all I really liked the F2, but decided to focus more on medium format so I sold it and went back to using my RB67. About a month ago I decided I need at least 1 good 35mm slr so I bought a Nikon F with FTn head. The meter works but I prefer to meter by hand with my Gossen Luna Pro F. So far I couldn't be happier than I am with the F and the Nikkor H.C 50mm F2. Some would say the F is lacking compared to the F2 but really all I've given up is 1/2000 top speed, better mirror lockup on the F2, and 2-10 second shutter speeds. I honestly think I can live without them, plus I kind of like the removable back, and don't find it to be a pain like some do. The FM2 just felt cheap to me when compared to the F, and F2, just really not my style, I'm sure there excellant cameras but not for me. Plus I love good cheap non ai lenses, and stop down metering is not my thing.
The various F2 models are the same body (or essentially, so, some small tweaks may have been introduced over the years), with the prism determining the model.
If you are really after the "execellence on mechanical technology", I can only repeat my Leicaflex SL reccomendation. It really is a step above the F2 and the F.
The SL2 is even more of a mechanical marvel, but would be over budget.
As pointed out, lenses will usually be more expensive than Nikon ones, though not as much as legend has it.
Re Spotmatic: lovely camera, but viewfinder is a bit dark. Also, if you change lenses often, screw mount is a PITA.
Also, depending on which lenses you're using on your Contax and Rolleiflex, you might find Nikon lenses to be a step down, though if you choose very wisely, that can be minimized. Unfortunately Rolleiflex's mechanical SLRs (SL-35 and SL-35M) are neither jewels nor tanks. While not a mechanical jewel by any means,your SL-35E is actually a very sweet camera - as long as it keeps working. I use mine a lot!
I've read many times that the Leica slrs have silvering problems in their prisms
By corrugated do you mean the honeycomb titanium shutters?
Yup. that's the one. I've replaced a bunch of them with the later smooth blades. Usually it is only one of the curtains that need replacing; however, I would replace both of them. Apparently the blades would "whip", distort, of something similar due to the strong spring force exerted. The curtain travel time with those shutters was much faster than that of the FM and FE. It was about a 65$ repair. I didn't replace the whole shutter.
For some. Finding a mechanic for a Contarex gets a bit difficult, but that's due to a lack of spare parts. Finding a mechanic is simple. Finding a good mechanic is not too difficult. Finding a mechanic who is ready to repair a camera for a price below the market value of many cameras is difficult, but that's not the problem of a lack of mechanics. Many popular cameras like the Canon A1, AE-1 etc., many Minoltas and Pentaxes like the ME/MX, many Olympus OM cameras and many more are simply too cheap to get a repair. I can buy a working, serviced Canon A1 for 20-50 Euros, and that often includes 1-2 lenses. What if it fails? Repairing it is a waste of money, most people say. There is not a lack of mechanics, there is a lack of demand for time-consuming and cost-intensive repairs.
For cameras with a higher market value like Nikons, Leicas and Rolleiflex cameras I can choose from a long list of repair shops. Some are better, some are not so good, and I think they will survive because people are ready to pay an acceptable price for a Leica M CLA or similar jobs.
I don't know what the exchange rate between euros and dollars is, but my average charge for the cameras you mentioned was $45 USD or less.