well depending on what you want your amp to do.. 2 channel or 4 channel amp.. here's choices
1) make your amp run your component speakers only and your aftermarket deck run the rear speakers
2) let your amp run both component /aftermarket speakers.. that will need a 4 channel amp if you dont know.
I am running type s right now as mention above and i am running 350watt amp to my component speakers and my aftermarket headunti(alpine btw) is running my rear speakers, than I have jl audio 1000watt amp to run my jl 10w3 sub.. its a nice set up, sub/ was most expensive out of my set up. 350 watt would do the trick, any other questions? feel free to ask, cause I have the set up your going with.
Edit: should also mention rear speakers are way over rated in our cars! you wont hear them at all, unless you use the back seat alot and want your friends or whoever to hear music..