I see you are hooked!
I had an FM3a but sold it - a lovely camera but I couldn't really justify carrying around £300-400 worth of body when a £100 FE2 does exactly the same thing (minus the ability to work without batteries, which is pretty pointless really). If you like that style of camera, then an FE2 (or FM2n, if you prefer manual exposure control, LEDs etc) is probably a better bet.
One problem I have with my FE2 is that I wear glasses and can't really see the whole viewfinder in one go (this is true also of the FG and its ilk). The F3HP (or regular F3) is so much better in that regard. If you don't wear glasses, then it probably won't be an issue.
The F3 is slightly more bulky/heavier, has a 100% viewfinder, and a lovely winding action, and a myriad of accessories. If you use flash, it's a bit of a fiddle, and is a bit hampered by its slow 1/80 (I think) flash sync. On that front, you're much better off with an FE2 or FM3a which have TTL control and a 1/250 sync. For me it's pretty irrelevant though.
There are of course lots of other options - F2, F4, FA, FE etc depending on how you intend to use them could be the best option for you.
Alternatively, just get on with buying one or two, see how you like them, and sell them if you don't get on...it's part of the fun of film photography for me, trying out the different options without spending a fortune, as you can usually get your money back when you sell them on anyway. I've had all of the above (and more) at some time or another!
The other thing to think about if you're looking to spend money is to invest in a few lenses, to go with your 50mm. Maybe a wide angle such as a Nikkor 24mm f2.8 perhaps, or the classic Nikon portrait lens, the 105mm f2.5 ? If you get them in AI or AI-S fitting they'll be a perfect match for whichever of these bodies you go for.