Dynavector 20 Xl , Benz Micro Ace SL or Denon

I have owned a P25 and now own a VPI Scout. On the P25 I had an Ortofon MC2 and then upgraded to a Lyra Dorian. The MC2 to Dorian was a nice upgrade. But changing to the VPI was a much bigger step. I'm not saying that you should buy a VPI.
However I am sugesting that you safe your money and buy a better turntable. IMHO that will give you better bang for buck.

Have you tried using a seperate phono pre?

I think the list is:
1 turn table
2 phono pre
3 arm
4 cart
5 cables

Nah, buying a better TT he has to buy a new cart anyway!!! then its 3thousand plus..Geez..
As for your question: the Dynavector is very tall.. so you may need to raise the arm base a 3 or 4mm to maintain VTL. The Benz is good, (I have a Benz glider medium output on my P5 and it is a wonderful combination, the Micro Ace on your P3 would be just right, though I would get the medium output as one needs an exceptional phono section to use a low level Benz without noise. (You might also need to raise the armbase 2mm with the Benz, I have to raise mine 2mm for better VTA) The Rega cover should handle up to a 4mm increase in armbase height.
A lot of folks use and like the Denons.. but I have no experience with a Denon cart. (the Denon probably would not need an arm base height adjust.)

The Denon 304 is very good, I have one on my Aries with 12.7 arm. The AT 33 is also a good cartridge, I just got one for $400 at J&R. I got the EV version, also comes as the 33 PTG or something, could never find out what the difference was. You might consider a VTA adjustment base for the Rega, which is a good arm. VPI and Michell and others make them. Don't tell Raul but I find that MCs give more detail than MMs and a better sound stage.

I also have a Benz glider on a P-5. Before this I had an Exact2 on there. Night and day difference. I also had the P3 before upgrading to the P5. The P-3 is a good table and deserves a nice cart!