What benefits to expect from tonearm upgrade

Depends on the tonearm!!

Petermax
I'd really like to listen to a tonearm that will trounce a rega rb300 (in every respect.

Replace your Rega with a Basis Vector. I did and the experience was eye and ear opening.

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...

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.