I bought this combo to replace the original pipe and silencer. I had already fixed dents in my old pipe several times and after the last damage I finally figured it was time to replace. I like riding technical trails and have bought the Gnarly pipe in the past, but I never cared for the bends on the Gnarly because it seems to stick out more than the stock pipe (which looks funny and makes it more prone to getting dinged up). So this time I went with a Fatty instead. The pipe is definitely made with stronger material than the stock and seems like it won't dent as easily. The profile is still tucked in close to the bike (not as much as stock but tighter than Gnarly). The nickel plated finish is really nice. I can't say if the pipe performs any better than the stock but it was a definite improvement from my dinged up pipe. My bike was lagging on the bottom and now it feels peppy again. I can easily lift the front wheel to get over large obstacles. The top end also feels like I can be a contender on the track. The only negative comment I have is the fitment. The bolt near the rear didn't line up correctly. I had to put the bolt in from the reverse side of the hole to get it mounted.
The KTM stock silencer on the XCW was already rather quiet so the Q-Stealth wasn't really an improvement for volume. The Q-Stealth is actually larger than the stock so for me its more prone to damage, however the bike does look more tricked out. Replacing the packing on Q-Stealth will be take a little longer than on the stock KTM silencer. The KTM uses a single large screw to secure the cover, whereas the Q-Stealth uses rivets.
Overall, I'm happy that I bought the combo. The bike feels like it did when I first bought it and it looks tricked out. I would definately recommend the Fatty over the stock. As far as the Q-Stealth, I think that depends on what you already have and what you want to have. If it wasn't for the fitment issue I would have given 5 stars.