Help My wife bought me a sub

My wonderful wife bought me a used but well cared for SVS CS-Ultra subwoofer for Christmas, which was very cool. However, she didn’t know about passive vs. active subs and I don’t have an amp (the RDA-7 does not have a sub output) to drive the passive CS-Ultra. If I was going to buy an amp I’ve read that a Crown K1 might be a good choice, which I’ve seen used for around $700.

I have a dedicated room which is small, 12’10” x 9’ 5” x 7’ 10”. Mostly used for TV but want a high level of satisfaction for movie/concert video’s when I do watch. No critical music listening done since I have a separate room for my 2-channel for that. I currently do not have a sub but have been looking, just hadn’t pulled the trigger yet.

While I’ve read that the CS-Ultra is a very fine sub the drawbacks I see compared to active subs are no amp, no electronic adjustable characteristics like phase, gain, EQ, etc.

Active subs I had entertained were the SVS PC-Plus or PC-Ultra, Onix Rocket UFW-10, Hsu VTF3 Mk 2, or something along those lines. I have a balanced output connection from the RDC-7 processor and would like to use it if possible.

I’m thinking that if I did sell the CS-Ultra along with the money I didn’t spend on a Crown K1 amp I would have plenty to buy a really nice active sub that would give me all the electronic adjustable bits I think I need.

The components I’m using are Integra Research RDC-7 processor and RDA-7 amp, NHT M5 L/C/R speakers. No surround speakers yet.

What to do? Any advice or suggestions would be most welcomed!