Does this sound decent?

Ok, I have a 1988 ford ranger single cab which has 4" speakers in the dash and 5's firing right into the foam of the bench seat. I have recently purchased an new head unit and a set of infinity reference speakers. Now my plan was to get about a 200 watt amp and bridge the rear channels and put an 8" sub behind the bench. The 4" speakers would be blocked below say 150 hz and the sub would be blocked above 200hz. I do not have any kick panel, or door panel room to play with so this was my best solution. I do not want a DB system or one that will aid in my deafening, just a nice full sound for my planned carpc, and HU. Any recommendations on amp+sub combo's, or even better ideas than i have come up would be appreciated. Thanks in advance

Budget?

Around say 500$

your saying you would bridge the rear channels so you want to run a four channel amp i would not recommend running your front mains and your sub off the same amp  i would suggest a small 2 channel for the fronts and a small mono block for the sub  maybe alpine checkout www.ikesound.com with your budget and what your going to need this site might help1974 ford pinto 4 15" punch Z power punch bd 1001 pioneer DEH-6700