What about aftermarket forks and rear shocks?
Most current sportbikes have very high quality suspension, both front and rear, that until recently was only dreamed about by the average rider or racer. Cartridge forks and remote reservoir rear shocks gained widespread use in the mid-ninties. A cartridge fork is essential for the performance minded rider. The presence of external damping or preload adjusters is not very important since proper tuning will archive the desired results. Some top racers feel the need to upgrade their forks to one of the several types of Ohlins Forks, or swap the entire fork cartridge assembly with a K-tech or GP Suspension cartridge unit. While these are beautiful examples of the state of the art, they are far outside the performance needs of most riders or even most racers. Ebay has become THE place to find OEM fork upgrades from other bike models. For riders stuck with the older damper rod forks, Race Tech makes a Cartridge Emulator that can significantly improve the performance of the stock fork.
Two major players are in the rear shock market, Ohlins and Penske Racing Shocks . Other manufactures do exist in this market, but these two are unquestionably at the top. Ohlins has been producing very high quality suspension products for a long time. Penske is fairly new to the motorcycle market, but brings years of knowledge from their domination in almost every other form of auto racing. Many valid reasons exist to replace a stock rear shock: the need to service an unserviceable stock unit, to change springs when none are available for the stock unit , to gain advanced damping adjustment features. One of the most desirable traits of the aftermarket rear shock is the ability to adjust to different 'eye to eye' lengths. Some stock bikes may have this feature, or what is known as "Ride Height Adjustment", but most do not. This gives the tuner the ability to change the bikes geometry from the rear of the bike, affecting not only steering angle and trail, but more importantly squat behavior.
I highly recommend the Penske Racing Shocks. They provide for a level of tuning unavailable on the Ohlins unit (16 different piston types), they are often cheaper, they can be ordered with the proper spring, they are located in USA and the tech guys speak english, and they do not come in a tacky gold color.