If you want to connect an amp to the front and rears, then you will be limiting yourself because now you have to buy a 4 channel, when only a 2 channel was nessacary. For the money you would now have to spend, getting a 4 channel, would have got you a really nice 2 channel, you properly drive your front splits. It's always reccomended if it's within your budget to get a seperate amp for your sub. A mono block amp, is what you'll be after ideally, and by using a seperate amp, you will have greater tuning options available to you, once it's all installed..