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.
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.