Crazy thought - rather than upgrading the cartridge, have you considered upgrading the 309 to a Series V?
I used a 309 for nearly 15 years and always loved it. I felt it was about 80% as good as a V, until I finally bought one a few months back.
I would now revise that figure to about 60%…
Interesting, did you make use of the damping on the SME V ?