Sub box for Coupe

[notaverage]

I have the bose system and I had my amp installed. I usually do my audio work myself but didn't want to risk anything on my first new car. After seeing what Ultimate electronics did, I could have done it myself. All they did was tap a high/low converter off of my rear speakers. I was under the impression that there was something special you had to do but I guess I was wrong.

So if you tap a high/low converter off of your rear speakers, does that mean that you don't need to remove your factory head unit/navi for the install? What I mean is, can you just get the audio signal from the wires of the back speakers? Any extra details you can offer me would be great! I really want to do the audio install myself if it is easy, I've never done one before, so I need lots of help

Thanks in advance

[notaverage]

What do you guys think of this setup??

http://www.costco.com/Browse/P...opnav=

It's from costco, so price is probably good, and no problems with returns and stuff.

Anyone wanna school me on subs, amps, and enclosures? Would be greatly appreciated