Can it be done without a preamp?

I have a pair of Classe Cam350 monoblocks running directly from an Audio Aero Capitole CD player. There is no preamp in my setup.

Is it possible to connect a subwoofer to this setup since I don't have a preamp. Subwoofer would be used for two-channel only. I'm considering a Revel B-15 to add to my Revel Salons and improve the bass response.

REL subs could be used in your system. They can be connected from your amps binding posts to the sub. In fact this is the preferred connection according to REL.
player has RCA and balanced outputs I run the RCA output to the main speaker amplifiers and the balanced to the woofer/crossover amplifier on my Genesis 200 speakers. The output signal level is the same from both outputs