I'm Looking to upgrade the stock ST1 Focus st sound system. I'm thinking about getting these Infinity Kappa 60.11CS 6-3/4 6.5 speakers for the front and the back. what kind of amp should i get?https://www.amazon.com/Infinity-Kappa-60-11CS-component-speaker/dp/B00B41LZ1M/ref=sr_1_1?keywords=Infinity+Kappa+60.11CS+6-3%2F4&qid=1555288161&s=electronics&sr=1-1-catcorr Could possibly add a sub, a single 10in. so maybe 5 channel or 2 separate amps? Thanks for all the help!