What kind sub will connect to Mark Levinson 383?

Most powered subs will have line inputs and speaker level inputs. In addition to the wires you're running to your satelites, run some 12ga wire from the 383's speaker posts to the subs speaker level input. Some people prefer this method even when they have line outs from their pre. Good luck.

I believe any of the REL Subs will work magic for you, i know for sure the Storm III and Strata III both have high level inputs and come with the proper cable you will need, and both are very nice subs.
Good luck!

surely clouded the issue. My understading was most subs nowadays are made for home theater application and therefore will not require the high level input.

And why would anyone want to hang another piece wire to the apeaker output path is a mystery to me.

I may be wrong in my assement, please feel free to correct me.