This. Civics might be "played out" but are still a fantastic means of transportation, easy to work on and cheap to fix. As long as you don't put a coffee can exhaust on it or stupid rims, etc. nobody will think you're a tool for driving a DX.
As for systems, I've had little and I've had insane. I'd err on the side of moderation though if my opinion matters, overkill rarely sounds balanced and it's really just obnoxious. A decent 10" sub will give you the low bass but not take up a ton of room so I'd roll with that, personally.
Infinity speakers w/500w amp
(2) 12'' Pioneer subs @ 4 omhs being pushed by a 1400w amp