I also love the DR roundcore strings, and have had good experiences with them on G&L basses and my lone, remaining Fender. The Pure Blues and Sunbeams are great, and I agree Sunbeams are good for scooped sounding basses because I've loved them on my Fender J. They sound nice and fat, but not muddy. The Pure Blues have been excellent on my G&L JB-5. (I also love the guitar Pure Blues on my G&L Comanche.) On my SB-2, Fat Beams have been my favorite DR strings, but it now has either Fodera or Sadowsky strings, which are also excellent. Wish I could remember which.
But back to the M-2500. It came wearing D'Addarios like all G&L basses, but the shop packed the case with three sets of Dean Markley strings. Best case candy ever. I first tried the Helix, which were excellent, but those have been discontinued. It now has SR2000, and they are fantastic, perhaps even better than the Helix. Great feel, clarity, and excellent balance without sounding bland. They have some "life" in the tone, and worked well for a recording project. Highly recommended, and I bet they'd be great on other MFD-loaded basses.
SR2000™ Bass Strings