what subs are good subs???

Ok I want to get some subs right I don't know much about subs though. All I know is my friends visoniks and autiobahns sounded great and never had any problem with them. I want to get some pretty decent subs but not for alot of money maybe around 300 for 12's what should I get any suggestions. Another thing what should I look for when I buy subs like what makes a sub crappy and what makes them good. If anyone is sponsored with subs like what kind of sponsorship did you get. Polka audio and Visonik are both interested in sponsoring me but I'm not sure what kind of deal you get with subs I don't want to do it unless I'm gonna get at least 4 subs and an amp

4x12's for 300 is gonna be hard 2 do, go look around the threads on this forum to get some ideas. both of those companies arent all that amazing