What benefits to expect from tonearm upgrade

Dear all,
Seems that it's time to upgrade my 5+ years old ortofon as212s arm.

To be honest I am quite skeptic on the benefits of tonearm upgrade based on some demo that I listened to. Unlike cartridge or table.

If, for example, I upgrade to $ 5,000 or more tonearm, and say it matches very well with my cartride (lyra kleos) and my table (TW Raven One).
Is the benefit audible? In what way?

Thanks in advance for any advice
All high quality tonearms will improve with a better cartridge.The cartridge (correctly matched to a tonearm) will make the bigger improvement.Many years ago, a reviewer (if I remember well it was Alvin Gold in HNRR magazine)reviewed the RB300 and he prefered it to the much more expensive Zeta that was considered a reference back then.He also commended on the reasons why many dealers recommended the Zeta , presumably for profit reasons.Without a listening test on your turntable and cartridge you cannot be certain which tonearm will sound best.Not to mention that if we take vfm into consideration,things are much different,and certainly in favor of a better cartridge,even turntable...or phono preamp.
Many people regard the RB300 as being a very solid foundation, though with some room for improvements due to compromises made to reach its price point. You see mods for these arms more than for any others. Some of these are DIY kits for just rewiring. Origin Live also has more comprehensive mods, IIRC. Currently one of the more highly regarded modded Regas is the Audiomods arm. Had an RB300 and the improvement when I moved to the Audiomods was significant. And I experienced a significant improvement when I moved up to a Moerch DP-6 and then DP-8.

But yes, Petermax does make a good point that it is important to gauge what improvement will get you the most bang for your buck.
Thanks for all of the insights,
How about if I rephrase my question..... Theoritically.... What audible improvement to be expexted from moving from an "okay" tonearm to an "excellent" tonearm.

Jperry has mentioned imaging, does it mean better "placement of instruments" or bigger soundstage? Is there any other else?

Please when somebody mentions in technical/measurement terms, what will be the audible impact of that better technical/measurement.

Thanks again
I found that tonearm improvement - even with the very best arms are not dramatic...better tracking, cleaner, clearer presentation, etc.. differences that will make you smile, not jump for joy.
Without the right tonearm you will never realize the potential of your cartridge or turntable. Unless both are very subpar, get the great tonearm first.