Best cartridge for an MMT arm

Hi-I recently purchased what I hope is my last turntable-a Roksan Xerxes 10-with the big outboard power supply, the upgraded speed selector, etc. Previously, I was using a VPI junior with the Rega RB300 arm-I had switched to a high-output moving magnet cartridge, Regas Super Elyse-nice, although its output tended to overload phono preamps. I still like this cartridge, but it sometimes isn't a perfect match for the arm-there is some sibilance at the inner grove area on some recordings-and this never occured when the RB300 was used. Yes, the two were well matched-I want to go with a great MC (I have Roksan's artaxerxes phono preamp, and am happy with that)-I loved the Dynavector 20x, and the older version of the Benz Glider-any experience using those two cartridges in my MMT? I'm not going to replace the arm-I've heard it side-by-side with the 309, and it is at least as good-and I dig the removeble headshell-I also have another table (Thorens 160 Super) with the same arm. I'm almost in Analog Heaven-one more cartridge buy and I'm there. Those 1100.00 and up cartridges are more than I wish to invest-they're good-but they're out of my budget. If it matters-my amp is a CJ premier 11a, and the speakers are Spendor SP 100s, connected with nice Nordost Superflatline MK something or another (bi-wired). My cats like the cable too, the little bastards (I fixed that in a humane way). Oops-I'm going off base here...thanks in advance for anyone's input.
Given your particular circumstances, I would go with as much Dynavector cartridge as you are willing to spend.
The 10x4 is a very nice sounding cartridge around $400. You could go higher to a 20x, or a 17d2 Karat. The compliances of these cartridges will be better suited to your arm, than the low compliance MC cartridges I usually recommend. If you want the stretch you budget to the max, take a look at the Benz-Micro LO-4. For a medium compliance cartridge, it is about the best at that $1k-$1200 price point. It retails for $1200, but you may be able to get it for noticeably less.

I know that you don't want to change arms, but I feel that it's important to tell you that for the same $1100, an Origin Live Silver Tonearm, and a Denon DL103R, will significantly outperform the MMT combined with any cartridge that you want to put on it. Unfortunately, the DL103R is too stiff and heavy for the MMT.

Your old RB300 arm is definitely superior to the MMT. The MMT was only about a $200 arm, and never was any competition to the RB300. The Origin Live Silver is worlds apart from either of them.