It probably is, and I do plan to add a sub down the road; however on a budget such as mine it's just not practical to cut back on everything else to afford a sub and build a box (or cut at the car - which I don't really wanna do)

Though, I am intrigued, how wouldn't it require a seperate amp? Maybe I just do'nt know what I'm talking about - which is true in itself - but if I'm buying a 4x100 amp, to power my 4 in-car speakers, how am I going to power a seperate amp? the 50w that the deck will put out?