One important thing that you do need to ask yourself is what will i be doing with it, playing games at what res? even a GTX750ti can handle 1080p, gpus like 780/970/980 imo are more meant for 1440 gaming or benching. Personally i think the upcoming gtx960 should be a very good option for 1080p gaming, even hard games, i feel its going to be the sweetspot, but too bad nvidia delayed the release to January so it doesn't cannibalized the GTX970.
The knobs or switches on the fortress in theory are built in the line of the fan, so its not like the the usual fan controllers, this are more like switches on the fan that were extended to the case, so its not the same case as the R4, where its a elementary fan controller that takes the power from the PSU molex and sends the undervolted signal to the fan via the fan controller. While its not totally different, in the case of the R4 you can swap fan and still use the controller, on the Silvertstone, you lose the fan you lose the switch, that if you are not into modding and do some splicing and soldering.
In terms of the best fans, i would recommend you to stay on 120mm, there are a vast amount of options, and a ton tested from SPCR, fans like Scythe Gentle Typhoon, Glidestream/Slipstream, Noiseblocker M12 S1/2, Noctua NF-S12A are really good fans, probably among the best tonally, even over 140s and 180s and 200mm, that said, but a bigger diameter fan will also push more air with less rpms (among other things). I personally have accepted the tradeoffs when i went with the R4, i wanted total control on PWM, i was fed up with issues with Asus issues, from soundcard pops, usb issues, and AI Suite has a very wierd way of measureing temps, that according to Asus is intentional, and they use their own algorithm to perdict a much more accurate CPU temp, that it will not match anything from another probe.... this is when i decided to dump asus and move to MSI, out of not having fanXpert2 i decided to go full PWM and thu the reason i ended with NF-A14PWM.
Now in theory there are two ways to achieve a quiet PC, either you don't produce the noise or you try to enclose it or mitigate it. Both aspects are mutually exclusive, but end up in the same path at the end. A more closed and dampened case, will be restrictive on airflow thus needing more rpms to equal the cooling, but the gain is noise isnt as freely let out, now a case more open will require less rpms as it will not be as restricted and thus you can have one of the noisiest components of today... fans, at much lower rpms thus ending with a quieter PC.... again both are very different approaches that can end up very similar. But its best to chose components that are quiet and later on decide whatever case you feel its better for your cooling needs.
Now about components you are considering,
ASUS GTX 980 STRIX (silent and probably coil whine free)
Asus tens to market their GPUs as coil free, and while i havent seen any newegg/amazon users reviews say anything different.... its not out of the subject. Check the following video, and while its not clear its asus gpus, as she is still trouble shooting, its just a mention for you to consider, Semi-Passive Gaming Build – GTX 980 970 780 Strix, i7 4790K, Noctua NH-D15, Corsair 730T, ROG Hero
Silverstone FT05 (looks nice, sound absorption, dust free due to positive pressure stuffs etc)
Here its up to you, and while cases do impact somewhat what gets out, in my experience it can be done with open cases as well, more importantly is to chose properly the other components to not be huge generators of noise. Personally i like the design from the FT02, although once you have fans it matters very little the orientation of the components, but for a semi passive setup might be worth it, specially if the PSU is semi passive and so is the GPU. But on the FT05 real gain more than the orientation is the 180mm fans, which are massive and at full rpms they cool like no other at the expense of noise, lowering them at sub 500rpms place them into a decent quiet setup, not silent but quiet, there are alternatives like AP182 that can be dropped off even further, but at expense of having it undervolted with the knob and with the motherboard aswell, here Asus or MSI should do it fine. Personally i wouldnt consider the FT05 for 140mm fans, for that i would go with another case, if you want open Corsair Air 540 would be my pick, or a more closed Fractal Desing Define R4. If you are interested on staying with 120mm fans, then consider NZXT 440 or Nanoxia DS1.
Scythe Kotetsu (SPCR king)
Not much to say, its the king atm for price and performance.
Corsair HX1000i (the 1000W version very much because its range of fanless operation, and the HXi series because a supposed coil whine free operation)
1000W is not even needed for a quad sli, a HX750i would be more than enough for a even a quad sli, really the new gen is very efficient, i would stay in the range of 750W just to have more options for the future, but 1000W imo is overdoing it to the extreme. Check Hardware.info Nvidia GeForce GTX 980 SLI / 3-way SLI / 4-way SLI review
. If your goal is a single GPU, drop to 500W-600W at the most, and you easily could power it with 450W, but we dont know how will future gen might be, so safer imo 500-600. A PSU like Kingwin LZP 550 would be my pick, reviewed and recommened by SPCR, should do fine with the GTX980.
2 x Phanteks 140SP (same level SPCR acoustics king Noctua P14) to replace the stock AP181 fans
I would go with the phanteks on an R4, but not on ft05.