I bet your Fed-2B will work fine and be fun to use the J-9 on. I've recently discovered J-9s, and they're as good as the 50mm J-3, very nice rendering. What I find interesting is the rising prices of Soviet Barnack style cameras, and falling for Leicas. The other day I searched for early Fed 1s and came up with several that had sold for over $150. Some over $200. The average was about $100. Then I searched for completed Leica IIIcs from the post-war period. Their average price (bodies only) was about $200.
The same is happening with the Jupiter lenses, which now go for about 75% of what a Canon, Zeiss, or Nikon Sonnar type go for.
Ten years ago when Leicas were $400 and up for a Barnack body, the $29 Feds and Zorki's were a good buy and substitute. Now that they are within $50-100 dollars of each other, I'd say go for a Leica or Canon at some point. Actually, the Canon IVSBs and Niccas and other Japanese clones go for MORE than the average IIIc now...