I will keep up the Audiogon tradition of giving advice you didn't ask for. Are you sure you need a sub? I was of the opinion that the JBL L100 Classics had great bass that was well-synced with the mid and tweeter of that classic speaker. You know best - I had two Rythmic subs and don't feel I need them anymore.
Sub suggestions please
I just got a pair of JBL L100 Classics (I have seen that they are controversial here, but I love the look, and am impressed with the sound...I'm a happy camper). They are connected to the Cambridge CXA61, and I run a Technics SL1600 with a Grado Prestige Green3 cart, and a Cambridge Alva Duo preamp, and Cambridge CD transport (CXC V2). My sub is a Klipsch Reference Series 12", which I like, but it doesn't aesthetically work with the JBLs. I'm considering the REL Classic 98, Sonus Faber Gravis II, or the SVS SB-3000 (I was told I could get it in a walnut veneer, but haven't actually seen that. Walnut is important in this case). Any seconds on one of those options? Any alternates I should consider at $1,500 or less (I am perfectly satisfied with pre-owned)?