Vinyl/TT Gurus Chime in! Cartridge Decision: Rework My old Sumiko or get a new cartridge?

Go with a retip.  As long as the cantilever and suspension are both in good shape and an actual retip is all that's needed, you should end up below $300 if you go with Soundsmith.  If it needs a full rebuild I would suggest going for the most expensive Boron/Contact Line option @ $450 + shipping.

I last had the same thing done less than a year ago and the result was simply superb. The re-built cartridge will likely sound a bit different, but certainly as good or better than anything you can pick up for $600 new.

I would try the retip process first Soundsmith does a fantastic job, if not try one of their MI cartridges.

The re-built cartridge will likely sound a bit different, but certainly as good or better than anything you can pick up for $600 new.

A retipped HOMC is still a HOMC.
High Output Moving Coil cartridges are inferior by default compared to LOMC (Low Output), but the problem is the OP's phono stage without MC input. 

What is really better with MM ONLY phono stage is MM or MI cartridge. 

@birdfan For under $600 there are many great MM or MI, mid compliance are ok for your arm. Instead of some hybrid you can get from retipper, i would recommend to look for a completely different MM cartridge, this is all you need for your phono stage (not a HOMC). Something like this. 

I have to disagree with the esteemed (sincerely) Chakster on a couple of points; not all. First, I completely agree that there are great vintage MM’s for under $600 that may be, if not necessarily “better”, better suited to your system’s tuning and your tastes; your call. What I don’t agree with is the suggestion that all HOMC’s are inferior to all LOMC’s. I have owned at least three HOMC’s that were decidedly better than at least three LO MC’s that I have also owned. Having said that, I agree that generally speaking most HOMC’s are inferior to GOOD (!) LOMC’s. However, the Sumiko Virtuoso B is a very good cartridge and one of the few exceptions to the rule. I have owned it and the even better Virtuoso DTI and they are very very good if you like what MC’s do well (the third was a VDH HOMC).  For a retip cost of under $500 it is definitely worth hanging on to. Very important to keep in mind that while it is HO, its output is still about half that of most MM’s at around 1.8 mv. Boron cantilever/VDH1 stylus, btw. Good luck.

I use to be a dealer for both Zeta & Sumiko and know those products well.

The first thing you should check is the arm. Some Zeta's had or developed sticky bearings - try a cheap new cartridge and verify that the the cartridge is the problem.

Secondly, if the arm is ok then what you should know is that the Talisman Virtuoso B is the only high output MC I would consider - I dont believe there are any cartidges for $500-600 retail that will better it. Therefore if you can get it rebuilt for up to $800 I would go for that option.

Otherwise I would look at a MI cartridge - Soundsmith cartridges are great vaue and good sounding across the board price wise. I prefer them to say the Ortofon Blue/Black MM range.

I would not recommend vintage cartridges - you cant get replacement styli in many instances and furthermore the damping rubber is unlikely to be in as new condition on a vintage cartridge.