Well, cheap = not as good. Like everyone says "You get what you pay for". Cheap is just means you pay the same amount eventually, because cheap goes out quicker. Lets say you bought a cheap subs and all went out at same time or not and you replace exactly same sub(s) it goes out again and the warranties even are worse. You end up going to pay in longer run the same as if you paid more the first time. Not saying pay your ass out for it. Just saying get something a little in middle of the line, then you should be a lot happier.
Cheap shows that your not set well.
Middle shows your doing something and have money saved.
Top of the line shows you either Rich or you just spent you whole life savings for it. Watch out for this one, because if you have people seeing this nice stuff plan on being jacked hard.
Brands to look for:
JL Audio Top
Rockford Fosgate Close to Top (Subs not so good as JL Audio)
Alpine is from Low to Top
Kicker
Hertz
Low end:
Power Acoustic
Sony Xplod except my Head Unit is cheap, but does real well. Had it almost two years now.
Kenwood except their higher end stuff.
Others I can't think of off hand.
There are others and other posters will say what they are. This is just what I prefer, if you are a local audio store shopper.