Yeah i have seen some crazy mods to drop noise,this build is going towards moderately quiet and its my first attempt.Doubt between my intel stock cooler and my 770 i could get htpc quiet but as long as i don't hear it over my speakers when i game or watch movies that is all that matters but that 80mm does make itself known.
I also want to go about covering up those side fan mounts, i was thinking large stickers to give my case some style while eliminating noise but i think it won't be all that simple but i do want a natural looking solution.
I'm trying to imagine the picture in your mind about this. Are you talking about the usual-access left side-panel? Some sort of bolts, nuts or nobby thingks . . . stickingk out of your case panel?
I didn't want to take the time with my drill press and my CM HAF side-panel -- to mod the holes for fan-support so they fit the NZXT 200mm fan. I just took some large purple wire ties and secured them so the little square thingie on the ends is pulled tight against the sheet metal exterior. I can't even tell if they're square -- standing several feet away. The ties loop through the fan's own corner holes which are offset maybe an eighth or 3/16" from the holes that fit the CM fan. The plus side I hadn't much thought about: they're less-than-solid plastic or nylon and they're not metal. I cut a gasket of 1/4" foam artboard to fit between the NZXT and the side-panel, but I could've used the AKASA rubber mats, and the gasket could have been cut closer to size and shape of the fan shroud.
If someone wanted to get into a day's modding project, for something like the HAF or maybe just a different make of case with only 140mm fan holes, you could probably (carefully -- with a punch-marker and drill press) widen the circle of vent holes for the larger fan.
Next level of tedium in the mod: run down to your local "metals" store (usually located in that part of town containing repair-shops, electronics wholesale for tradesmen, maybe lumberyards). Get some lengths of right-angle aluminum pieces to build a fan-sized frame, pop-rivet it together, drill the holes for the fan you want to fit, and then pop-rivet -- no -- SCREW it to your case bottom flush to the edge where the case panel slides -- maybe with a little clearance for the panel slides and hooks that secure it. You don't want it vibrating against the case. You could even rubberize the pop-rivets or screws the secure it to the case-bottom-edge.
The only thing better than that is a fan-frame constructed of Lexan to swing on a muffled hinge like that in the CoolerMaster midtower Stacker case. Geesh! Dawns on me you'd want to be able to pull the entire thing quickly from the case, so you might tap 6-32 holes in the case metal and use ornate little thumb-screws to secure the frame. You could still rubberize the mounting points.
If there were a gap between side-panel and the assembly, you could make a rubber (Akasa pad) gasket to stick on the case panel interior in the shape of the fan shroud. That would assure no leakage of interior air, and further muffle vibration.
Depends on how much time you want to spend and how much the pay-off matters to you.
That's why I just went for the wire-tie solution . . .