You're obviously not going for a high-end solution, since you're going with a compact sub instead of a regular one, so I think you be satisfied with the little extra punch no matter which one you choose...
If by "high-end" you mean big boxes in the trunk with huge amps and window-breaking basses, neon-lights, flashy wiring, speakers with chrome grills all over: no I don't.
For me a sound system has to be good, but discreet. So I'd like to have a "higher-end" sound all together. First I'll see what an added sub will (not) do for me, and then I might consider changing the stock speakers anyway, despite my previous post. I want the system to sound better, not neccessarily louder. The stock speakers are not that bad, just not well balanced. And they are obviously not designed for good bass response.
Best solution would be to go to a decent car-hifi shop and just test one of these compact subwoofers, but there are few car-hifi shops around here that let you test their stuff, and they are just a bit to "chavy" for me. So far I only found one compact sub, from BOSS, and it was IMHO overpriced and underperforming.