Very interested to hear where you go with an SPU. I'm in the same boat. I'll be trying a Ortofon SL15 and a DL103 on the arm and eventually a Micro Acoustics 3002 but I really bought it for an SPU but I have no idea which one.
I really like the basic spu classic gm mk ii — conical needle. Ive used two over 8 years. Ive tried more expensive ones and monos but they disappointed.
Some of the vintage ones from the 50-60s are probably really good but thats expert territory and i dont have any insights.
Enjoy with a good sut and valve phonostage. I use ikeda and abbas.