Well you need to measure what can either fit in the trunk through the opening, or be ready to build into the trunk. Its a pain in the ass to build in the trunk, but you can utilize a ton more space. I have a 98 civic 4 dr, and I think mines a tad bigger than yours...you should be able to fit 2 12s in there though. As for subs...a sub will play whatever you tell it to, even the stuff it shouldnt. What hz range it can play is more based on the box and how you build it/design it vs what subs you put in the box. SQ is sound quality, which is alot more than just sounding clean. Focus on the design and what you can fit comfortably over a poor design.
I second this. You can make almost every sub sound good with a good box and hit any note Just depending on you box tuning.