Your input please: Using sub on 2 channel amp

I am using JM Lab Cobalt 820 on my tube amp & pre-amp. Sometimes I am missing a little bit of bass coming from my main speakers. Is it possible to add up subwoofer on my 2 channel system?

I am considering Sunfire subs which is around 1100. You think this could add up to what I am missing without degrading musical excitement?

Your comment and suggestion please.