I have a CAAD5 that had C'dale brand brakes. The awful-ness came from the excessive ammount of angle that the pads met the rim with. You have to basically bend the pad to get it to contact the rim. Look close at how your brakes meet the rim and you'll probably see the same.

I researched a bunch and found that there's very little/nothing that makes one brake stop better than another*, provided they're all properly aligned. Some of the expensive brakes are actually worse because they trade rigidity and stopping power for weight. Fancier brakes replace simple nylon bushings for ball bearings which improves the feel of the brakes but doesn't do much for stopping power.

So I decided to go with Shimano Sora brakes (and good quality pads). Looking at the mechanical drawings the brakes are the same, right down to the part number, as the Tiagra brakes. At the 105 level you get the nice feeling ball bearings. And as you step up the Shimano line you get more and more fancy stuff like forged parts that reduce weight.

The Sora brakes stop great. Huge improvement over the old brakes. Slap on some quality pads and you'll be good to go.

* assuming we're talking purely about dual pivots here...