Hi, Check HiFimart, HTstore, Jamsticks sites for subwoofers. The bottom line to pick subwoofers is on frequency range and power it can offer like example - 30Hz to 200Hz... The lower the first number, the better low effects it can produce...
Secondly, the output power - you need to look at continous power and not the dynamic power. Continous power of 100W would be good enough for 12*12 room and since 583 supports two subs - look to get another one (may be same model down the line) this way you will get smooth and even bass everwhere.. Dual is always better for sub.
Yamaha has only 50w output power - Audition it before deciding.
BIC is good too, check the frequency and get another one in the future.