Cartridge/arm matching

Hi. I have to admit I know next to nothing on this subject. I have a Rega RB 250 arm with a Shelter 501 mk 11 cartridge. There's been some suggestion that that may be a less than great match as it's a medium mass arm with a low compliance cartridge.

I'm on a very tight budget… don't really want to change the arm as I've rewired it with Cardas & bought an Expressimo Half Moon Heavyweigh counterweight (the latter made a massive positive difference). Would a Denon DL 103R be a better match for the arm?