Tonearms - SME 3012, Jelco, or Schick?

I would have a look at the Groovemaster. The best 3012, the 3012r, will be above your price range. I was not impressed with the Jelco 750L, but there was an 850, in your price range, on USAM a few days ago, may still be there. The Schick is also a good sounding arm.

Will your primary cartridge be an SPU, as this would be a determinant of the recommendation?

Audiomods has released a 12" version of the Series Six that is excellent also. There are additional refinements to the design other than adding 2 or 3 inches of arm tube. I acquired one and it is my second favorite arm. 

Ortofon also

I owned an SME 3009, no experience with the long version or the other two.

Satisfied my long arm itch with a very long 12.5" effective arm from Russia. Unfortunately it has a fixed headshell, and the height adjustment is via set screws like the SME (mine made precise via micrometer provided). Your 3 choices all use the set screw method, not ideal for sure.

After changing from a single to a setup with 3 tonearms, the arm I like most is a removable headshell for alternate pre-mounted cartridges (including friends cartridges played here), combined with arm height/VTA refinement while playing (loosen/up or dn/lock by hand, no tools required).

505L on eBay

I suggest you have a good look at Micro Seiki 505L, which is a compromise effective length of 11-1/8", with superb adjustment features, VTA while playing, and it’s headshell fitting allows Azimuth adjustment.

I installed two 505’s on a wonderful Luxman PD-444 TT for a friend, learned what to ask about/avoid, if you look for one, write me a private message.

btw, think long: have you considered the potential of two arms? If you listen to Jazz, there are so many wonderful Mono LPs, it is wonderful having the advantage of a true Mono Cartridge ready to go.