Here are my thoughts on the kits and Dayton in general. ShadyJ has also recommended these kits as good value for the money. I have to say that I must disagree. I've helped someone build two subwoofer kits from Dayton, I've also built a two-way bookshelf using Dayton prefinished cabinets for myself, I've used Dayton resistors, banana plugs, etc. And I think they are one of the worst audio manufacturers around. Do they offer inexpensive parts? Sure. Are they of even the most basic acceptable quality? Mostly not.
The MDF they use is super cheap and brittle. The vinyl, or painted finishes are just simply bad. The paint on the front baffles wears of by the time you screw in the drivers. The vinyl bubbles and splits in corners. Their banana connectors are cast from cheap brittle metal. Even the screw threads are cast. They strip and crack even if hand tightened with a small plastic handle watch screwdriver. Most of their designs are blatantly stolen from Scan-Speak, WBT, etc. And they pride themselves for doing it. Both Usher and Dayton have publicly said that they stole designs from Scan-Speak. And these people don't care.
The prefinished subwoofer cabinets are extremely flimsy. They vibrate, creak, crackle, etc. The subwoofer amps have such cheap parts that they are not even labeled (capacitors for example). Most certainly cheap, fake components from China. There are many reports of these amps humming, failing, etc. Although the ones I've helped built are still working after 2 years.
Now let's take the budget SVS subwoofers in comparison. They too look like they have been built on a small budget, but the basic design is done extremely well. The cabinets are solid where they need to be. Braced where they need to be. The drivers are Peerless based. The amps have decent quality parts in them and there's hardly any reports on them failing. The finish is vinyl, but flawlessly applied. It's all these little things that add up and make for a very solid product, even though it was built inexpensively. I like that.
There are many drivers (Peerless, TC Sounds, Scan-Speak, Dayton, etc.) and amps one can buy for a DIY project, but by the time a half decent box with a half decent finish is built, we are now in the mid HSU/Outlaw/SVS price range.