Amp and Sub Install question

I have a Pioneer DEH4600MP HU with 4 speakers connected to it currently installed in a 97 Ford F150. I want to add a sub amp to my setup while maintaing all 4 of my other speakers. I have a budget of about $500 to work with. What would you recommend and how would you hook it up? The Pioneer has 2 sets of rca outputs and no sub output. Please help.

Thanks
Mark

you can just add a good set of RCAs to one of the low level outputs from the Pioneer.(usually the rear for subs). Shop around for whats in your budget for a good clean 2 channel amp or a decent mono bass amp. either way , then decide if you want subs for high spl or sq . are you looking for  8s?  10s?  12s. Is it a single cab or extended cab?

It is an extended cab. I will probably go with 8s or possibly 10s. By adding the rca cables, woul it not not disconnect that portion of the HU anp? For example by adding the rca to the rear output, will it disconnect the rear channel of the HU amp?
Thanks

No , It wont cut off any power to the existing speakers. The Head Unit has its own built it mini amp to power the speaker lines and the RCAs have no wattage but only a small enough voltage to carry the signal thru the cables. So you can use them to supply the signal to your subs. I have a 99 F-150 extended cab with 4 Kicker comp. 10s but I have removed the back seat. You can buy a prefab box thats made to fit underneath the back for a pair of 10s but the box volume is small and limited. Just a suggestion.........Ive done a system where I unbolted the back seat and raised it up about 5 inches and used very long bolts to re-bolt the seat back down. This gave me x-tra 5 inches to build custome box with much deeper and louder bass and still had full use of the back seat.