Answers:
The Alpine Type-S subwoofers are actually a good buy for the money. I have installed a number of these in different vehicles and, when paired with a good amplifier, they actually hit really hard.
I would recommend against the Kenwood amplifier idea though. I have seen a number of Kenwood amplifiers running subwoofers develop problems after just a short period of time. I find some of the better subwoofer amplifiers are:
Memphis Audio, Kicker, JL Audio, and Alpine.
Other Answers:
Alpine have been making decent speakers for a long time now. That is, in my opinion, a decent value. If you are going to be upgrading your audio you will want to keep in mind that most companies design their products to compliment one another. If you find that you like the Alpine speakers I would suggest committing to them regarding amps, subs, etc... If you can you would want to get tweeters in the front, midrange in the door panels, and a sub in the back or if there is room under the driver and passenger seats.
So far i can't find the problem on it. Sound so clear, it so powerfull deep for vocal on movie or cd the mono amp make the power better. Good price for multimedia outthere,best center speaker after i look around. if you ask me alpine sucks. it think there quallity has gone down over the years. but thats just me. i dont think they sound good under 85 hz. but thats just me. here is what i tell everyone getting in to car audio, and what i wish someone would have told me. listen to anything and everything you can before you but anything. listen to the stuff at best buy and circut city then listen to speakers at speacialty shops. listen to everything so you can find out what sounds good to you. personally i like boston acoustics, and kenwood. i really think both alpine and jl are overated.but if you like alpine and jl more then boston and kenwood, then more power to you. its your system it should sound the way you want to hear it.
good luck
Alpine makes nice highs, but you can do a bit better for the price. As far as subs are concerned I'd highly recommend JL Audio or Memphis. They have been dominating stereo evets for years now, and they win for a reason. Ask any competitor. I've been competing for years so I've heard everything marketed and many that haven't been.
As far as the price and clarity of the Type S Alpines, it all depends on the box...as with most subs...choose the right box and you will be just fine with the Type 's. Remember...the only person that matters when it comes to how your system sounds is you.