I've just replaced my Arctic Cooling Freezer 7 Pro with the Xigmatek S1283 + Crossbow mounting kit. So for the benefit of the OP (if they're still interested) or anyone searching, here's what I found.
1. Definitely quieter than an AC F7 Pro.
2. Reduced my Q6600 fully loaded temps by around 10C - quite a surprise, I wasn't expecting that much.
3. The spoiler thing looked like it might not sit securely so I left it off - don't want to risk stray metal items dropping onto another component.
4. Don't know about anyone else, but I found installing the fan with the anti-vibration rubber mounts an almighty pain. Horrible system.
Well worth the money and time though.