Combing preamp with tube amp

[anybodyelse]

I want to add REL HT-1810 subs to my system. But they have only LFE, low-level RCA, or XLR input. Mine Cayin-CS55 only has a speaker out. And before I buy two of the REL Airship II for 350€ each. I thought I could buy a preamp like Denafrips Hestia, and connect the SUB via XLR and the Cayin via RCA to it. Does it make sense? Or is it a bad idea? What can i expect of mixing non tube preamp with a tube amp?

 

[anybodyelse]

You can use a speaker level to rca adapter for $40 or less.
Russound makes one ADP-1.2 and there are many less expensive ones.

Thanks will check very helpful.

 

[kappclark]

I run a RCA Y splitter off the preamp to feed the amp and the powered sub