Avid Single Digit Series...no questions ask...NONE.

Avid SD 7 - great price great stopping power
Avid SD SL - If you like titanium.
Avid SD Ultimates - more expensive probalby better.

If you want the best v-brake for the lowest price, its the SD 7. I've ridden all three, but i have SD7's on my other bike, they were great!

If you want the best performence, get some SD or FR Avid levers, makes a huge diff aswell