So my ol lady has been wanting me to put a small sub into my truck because she likes a little more bump from time to time.

I dont want to spend much money at all and probably just going to get a combination sub and box already installed from best buy. and id like to set on the floor in the center of the back seat

probably this one
http://www.bestbuy.com/site/Dual+-+B...4#BVRRWidgetID

I dont want to change the stock radio with the affinity speakers

CAn i do it fairly easily or is it going to take a ton of changes?????????

 

you will need an amplifier first of all to power a sub. also a connector that will split into your stock headunit wiring and go to the amp.

http://www.crutchfield.com/p_142SLC4...4.html?tp=2001

 

It's pretty easy if you aren't looking for some fancy setup. Besides the electrical wireing, you need a splitter like what VP64 linked too. You essentially just "tap" into the factory wireing and get an output to the sub. I did that on my last car because the sub output from the head unit sucked. I had no noticeable loss to the speakers, but I'm sure you are "stealing" a little bit of juice from them. My adapter used "T" type taps. I wished I'd have taken the time to solder them though. Lesson learned, I now solder all audio connections.

 

nathangfnd: you'll need what's called a "low level converter". you can also find it at best buy or any local stereo shop. you don't need to actually cut the speaker wires to tap in. radio shack sells a wire stripper that will split in the middle of a wire and pull the cover apart so you can splice into it. start with the gain on the converter all the way down, set your radio's volume as high as you will normally go, then you can adjust the gain on the amp and converter.
good luck