yes it is totally possible, no you will not get the tunability of an aftermarket deck but that does not necessarily mean it will sound bad. I have added them to many factory headunits with good results and some not so good. The only way to find out for yourself is to put one in. Go to the rear of the deck and splice into the rear speaker outputs +/- for left and right speakers then attach that to your line ouput converter (this should be all you need to run to the line output converter then attach the rcas for the amp to the line output converter and run them to the amp. Make sure that you do not put everything back together until you have tested it. Also make sure that you get the + and - wires correct or the signal will be very weak and not much use to you. To test that just unplug 1 rca if the sound from the sub gets louder you made a wiring mistake.

 

Just because it's expensive doesn't mean it's good....

And kicker is good if you're into SPL (getting loud). There are better options, but there are worse. For those who lean more towards wanting a system that sounds good, an SQ (sound quality) system, Kicker is not the way to go. Not bashing either way, I'm just stating what i think.

 

The point seems to be that yes, if you wish to do what you are describing you can do that with a line out converter

 

It depends what you're looking for. You can put a cheap sub, a cheap box, cheap amp and a LOC and you'll get bass. From my experience it's better to spend a little extra cuz you'll be much happier with the results. Even if you can find someone whos upgrading their deck. I got a pioneer a few years back and i know i'm planning to upgrade soon. It's not that it doesn't work well I just want something with more features. But compared to a stock deck it'd have a lot more control. Check the for sale area.