VPI Prime or Prime Signature?

Hi folks, I’ve got a VPI Classic and Lyra Delos cart. I would like to upgrade to a Prime or Prime Sig. If I go the Sig. route I would stick with the Delos. Or should I get the Prime with a costlier cart? Privilege problem I know, but would either be a significant upgrade over the Classic which sounds great? Phono stage is LKV, pre is AR ref 3, amp is AR Ref.75, speakers are soon to be Martin Logan. Thanks for your input!