You need 55-60 db of gain in your phonostage(yours is .65mv.) for your new cart. An outboard phonostage can be a significant upgrade from the onboard of your Yamaha.
Phono pre amp
I recently purchased a new TT a VPI Prime with a VDH DD2 special MC cartridge, I'm very happy. I still want to use my previous TT which was a Denon DP51F with a Ortofon MM2 Bronze cartridge. My VPI is plugged into the phono stage on my Yamaha AS2100. The question is, will I get more out of the VPI if I buy a (better) separate phono stage for the VPI and use the Yamaha phono stage for the Denon? If so, what phono pre amp would be good for the VPI?