What tonearm will better mine?


I have been running a 12" Jelco SA750L with an upgraded Decca Super Gold on a Garrard 401 for a few years. I'm happy with the sound and happy with my pre, power and speakers. (Croft 25R, EICO HF35s, -good tubes, Quad 57).
I keep hearing that my tonearm is a weak link even though it sounds pretty awesome to me. What would it take to replace the Jelco and make a significant improvement? What should I expect to hear better? Would I have to drill the massive plinth? Thanks.
128x128noromance
@stringreen I don't care. They weren't criticizing, they were critiquing. Which is fine by me. Anyhow that was 2 years ago. I now know my rig sounds as good as many costing a lot more. 
noromance 
Glad to hear you made a tonearm change with a great result.

I bought an Audiosilente idler wheel based on your comments and it was a nice upgrade.

Thanks.

Jim Perry
@jperry 
Thanks Jim. Yes. I've since changed the AS idler for an Artisan Fidelity wheel. Not cheap at $400 inc. shipping and not as dramatic an improvement as the AS over the rubber original. Nevertheless, it tuned and brought more air to the bass and increased dimensionality and top end inner detail. 

@tzh21y
 Yes. The Jelco is quite good. Have you heard the 850?