this lil guy should suit your needs
https://www.amazon.com/Taramps-HS2000X3-Class-1X1600W-Amplifier/dp/B00O2WI1DK/ref=sr_1_7?s=car&ie=UTF8&qid=1502327289&sr=1-7&refinements=p_n_feature_keywords_six_browse-bin%3A7933266011
get a dual 4 ohm sub in a ported box and some decent front speakers and youll be off to the races.
Some Civics of that generation have seperate mids and tweets, some are just with the 6.5 door speakers, either way the door speakers will be 6.5s. Now, the brand and model of speakers and subs will be up to much debate, as will the amp and there is a headspinning number of ways you can get all this done. To get the best sound, youre going to want to do whats called an "active crossover" setup on your front stage which will require a 4 channel amp and rule out the one i suggested making it pretty much necessary to run 2 amps, and thats provided that you have the seperate tweeter pods or are willing to go thru the trouble of mounting tweeters separately if you dont.
Before i get ahead of myself and likely add a serious amount of confusion here, we need to know (since youre admittedly new) how far down the rabbit hole do you want to go?
Whats your approximate budget?
What model of Civic do you have? (ex, lx, dx etc etc)
how much trunk room are you willing to give up for your subs?
How loud do you want to get?
Are you going to be doing this yourself? (will make a big difference in your budget, unless you have friends that can help)
whats the color of the sky?
What kind of music do you mainly listen to?
Do you want a DIN or double DIN radio?
What is the square root of pi?