This is the kind of response that drives me crazy! The word components doesn't just refer to your front-end speakers - it refers to your entire system and the individual pieces (components) that make it. Your sub is only 1 speaker to help your sq package - your desire to focus on the sub gives me an indication that you aren't really looking for sq, you are looking for a good sounding system that has really good bass. Not really sq or spl - just another system...
To focus on sq, you need to focus on your head unit and it's pre-outs, your processing and its effects, your wiring to distribute the sound as best it can with the cleanest signal, and your speakers and respective power to reproduce the sound as it was intended to be reproduced. So far, unless you have every other aspect covered (doubtful considering your sefl-proclaimed rookie status) I would step away from the subs and rethink your project.
Otherwise, don't post that you want a sq system, post that you want a system that sounds good with a sub that can make some good boom cheap.