Best Cartridge Match For Rega RB300 KRELL?????

Greeting's Audiogoner's,
upgrading cartridge using clearaudio Sigma, for past 5 years, want to move up to a Koetsu Black, Transfiguration or Lyra. I guess bottom line is what will work best with the Rega RB 300 arm, advice would be greatly appreciated*********One more thing any one out there farmiliar with Krell cartriges (comments). Again thanks as usual for your help.
Krell cartridges? No such animal!
They have not been made for years! Like 10 or 15 of them...
It seems to me that those cartridges are too expensive for a stock RB300, and that the money might be better spent on a new arm (or upgrading the RB300) and a slightly less expensive cartridge. I recently put a michell tecnoweight on my RB300 and it's a good upgrade, and many people swear that a quality rewire will work wonders on the RB300 (I replaced the external cable on my RB300 and it made a great difference).
I have seen Krell carts. on Ebay lately.