In a small room , I would be cautious about introducing any subwoofer into the equation.
First and foremost, first try out any quality sub on a dealer or buddy loaner ... You may be surprised that it is a step back overall with a boominess or a wooley overemphasis simply because of room acoustics in a smaller room and restricted speaker placement alternatives.
Subs for HT are one thing, but adding a sub for quality 2 channel is a difficult alchemy. The good ones are all well north of $1500 w/o prejudice to the acoustic issue above.
It's going to have to be a sealed enclosure rather than a ported one.
Google the reviews,
Vandersteen 2Wq and ATC are two that I would audition ... In that order.
Google the forums for their testimonials.
E.g. The Vandy has three 8" drivers instead of one big one and its external crossover accessory is easier to tailor to the gear and room parameters.