1. No, that only applies to 96-98 civics.

2. Yes, you can just add a amp for a sub, it would actually be bad to add a amp to your factory speakers since they can ususally only handle about 40w peak. As for the amp, what you asked about should work fine. Don't just go by the rated specs though for an amp, talk to someone who owns one. Some amp companies have inflated specs for power output.