What speakers convinced you that your mix needed changing? Any chance of using those speakers along with your Carvins?
Monitors are a tricky business and add on subs in a small room even more so. It all comes down to what do you trust?
No easy answer I'm afraid.
Personally I'd look for some thing that has tons of versatility cause matching a sub to a room is a crap shoot that you will probably lose unless you can set it up your way. Here's what I did:
I started with the power amp...a Crown xti 4000. The DSP in that thing is pretty comprehensive. Crossover points, Crossover slopes, EQ, Delay and more all very finely controlled via software called BandMix. Its free on the Crown website even if you bought the amp used.
I made sure that I wasn't going to end up with a "one note" sub so I got a flat, neutral, low distortion speaker (
https://www.parts-express.com/dayton-audio-rss265hf-8-10-reference-hf-subwoofer-8-ohm--295-442) that could do whatever I wanted it to. I built a sealed enclosure for a pair of them and called it a day. I can set the sub up to sound appropriate for anything and store that setting in one of 20 presets on the Crown. Home Theatre, Classical, Jazz, Dub, whatever.
This may sound like over kill but I assure you it isn't. You will need a sub to match your room AND do many styles when called upon. Your typical Guitar Center powered sub won't be able to keep up and will end up on Craigs List sooner than you think.
the sub
the amp
Oh and I paid 200 for the speakers (they were on sale), 400 for the Crown used (you can get lower powered XTI's for less) and way less than 100 bucks for the wood and paint. Total, less than 700, easily worth it for a sub that can inspire in any situation.
good luck!
