Subwoofer & pre amp


I like JL Audio subwoofer, had F113 for a brief period and thought it was better than Rel B1 & Stadium I used to own.

I now have a pre amp with only 1 set of output; JL only takes line leve input and no speaker level input. Short of using a Y-adaptor which will degrade sound more or less, will I be better off getting a Velodyne DD or Rel again? Either one will be physically larger than JL whcih could be an issue.

This sub will be 30% music & 70% HT, I normally don't use sub for music but like to have that option.
semi
YO can have most cable manufacturers make a cable with 2 runs, terminated at one RCA on one end and each one with an RCA at the other. A Y cable w/o the adapter. I've done it, will work just fine.
that will require buying new cables and long XLR IC are not "cheap", probably cost as much as a subwoofer.

Purist Audio sells Y-adapter for $300 and they openly admit it will degrade sound.

JL subwoofer has variable/fixed gain selection in front. According to the manual, fixed is used when volume is controlled by pre amp or processor. what about variable? my pre amp has RCA line out which has fixed output, can that be used?