For a pair of large Klipsch mains only a large sub or multiple smaller will do IMO. The RSW subs simply lack true deep bass extension that wil make a substantial gain in overall SQ(LF limited audio reproduction is reduced fidelity).
This said...
One Epik Conquest, dual JL AUdio f113'd, one eD 900 sub or dual SVS Ultra 13 would fit the bill. All will provide sound quality and output and extension to put a giant smile on your face.
HSU just released the new sealed sub,they have a promo for a four pack ~4K. Should be a killer setup. I will order two of the new HSU's !
For me multiple sealed beat a single huge ported. Ease of placement,stackability, can be disposed around the room to create a seamless ...uniform and smooth response. What you will not achieve witha single sub.
Multiples are always preffered to single units.
Klipsch,Dynaudio,Paradigm Signature,Pioneer Elite,Krell,Tenor Audio,Anthem Statement,SimAudio MOON,Parasound HALO,Bryston,ATI,Onkyo Integra,Denon,JL Audio,Sunfire,TC Sounds,Acoupower,QSC PowerLight,Crown iTech,Furman,Chang,PS Audio and more in the house.
Too much gear,never too much music.