Subwoofer to go with bottlehead system

I am looking for a reasonably priced subwoofer to go with a bottlehead foreplay III and paramour set up. I have a pair of omega ts33 speakers. I gather I can either run a Y cable out of the second outputs to the sub OR go preamp to sub to power amp (if the sub has output rcas). I have quite a small living room so I do not need anything too large, just something to add some extra under kick.

Thanks