I purchased one from ebay for my 2011 RT-S. I installed it and it made a slight difference. Tried it on my friends 2010 RT and there was a big difference. He just ordered Elka's for his so does not need the sway bar. I would be willing to sell it if anyone is interested. $125 includes shipping.
I have always been a bit confused by people saying if you upgrade the shocks you don't need the sway bar upgrade. That's like saying I've got apples so I don't need oranges.
Shocks and sway bar work together to improve suspension response and handling. They do 2 completely different jobs in 2 completely different ways.
Granted, if you have Elka's the improvement from a sway bar upgrade will not be as noticable, and vise-versa. But having both is definitely the best way to go.
Shocks work independently. Each shock spring pushing down on its respective wheel with the same force when going straight. In a turn, the outside shock spring pushes harder as it is compressed. The inside shock spring, though pushing with less force, is still exerting downward force, lifting the high side of the Spyder even higher and increasing lean angle. This is fine if you like more lean angle.
While shock springs are always pushing down no matter what, the sway bar is completely neutral and does nothing at all when riding straight ahead. The sway bar only comes into effect in a turn and its only function is to resist lean angle. It does this by transferring the down force energy of the outside wheel to up force energy on the inside wheel, and vise-versa.
In other words, the sway bar applies additional down force to the outside wheel, where it is needed, and resists the unneeded down force that the shock spring is exerting on the inside wheel, giving you less lean and a flatter stance in the turn. The harder you ride, or the higher the weight (like 2 up) the more sway bar effect you get.
Now it may be that BRP has stiffened up the OEM sway bar, and in this case I could see needing only a shock upgrade. But the best shocks in the world are not capable of overcoming a too weak sway bar.