I have a 07 600 Ho Iq (carb) and I put the SLP pipe and can on my sled. It sounds very nice, has that piped sound to it, but it is no louder than the stock set up. Performance wise there was a noticable increase off the bottom (it would pull the ski's off the ground from take off which it never did with stock set up) and continued to pull hard thru the mid range. I did not see any increase on the top end but possibly with the right conditions you would.
A thing to note is Polaris jets their sleds very rich from the factory to offer the best performance possible thru the widest conditions. SLP's recommended jetting sets the sled right at the edge giving you top performance but also right next to the point of being too lean.
SLP also recommends clutching changes which increase rpm from 7900-8100 to 8100-8400 which I believe is giving you the very slight increase on the top end.
My opinion is the SLP pipe is not worth the money at all. I believe all the SLP system gives you is a little weight savings and the rest of the performance is thru jetting and clutching which you can accomplish with the stock exhaust.
I am going back to the stock set up and selling my SLP system. To me it's not worth the money and I do not feel comfortable running my sled right on the edge. I rejetted my sled, with the SLP system on it, back to a richer state similar to factory settings and the performance was no different to the stock system.
My SLP system will be for sale if your interested. Too me, the $500 is not worth saving a few pounds.