I haven't seen any sagging with my NH-D15, I dont imagine thats even possible. Everything is bolted on very well. Graphics card depending on weight.. eh possible? My 670 is a bit lower than I'd like since my case doesnt have any support for video cards.
As for your parts, a couple things.
Your RAM and the D15. Its 40mm tall, this is going to get in the way of the second fan. However you can raise the fan up the extra 8mm to account for the height of the RAM. You're case has a 193mm clearance for CPU coolers so you're still within spec, its just something to be aware of. Also with the size of the cooler and your motherboard layout you may not have access to the 1x PCIe slot thats on the top.
Just your RAM. Why are you going 4x4GB for 16GB? You can go 2x8GB for less and keep the other two slots open if you decide to bump up to 32GB later.
Fans. You may have gone a bit nuts with them. You're case already has a 200mm front intake and a rear 140mm. If you really want to load up the 3 top fan mounts and the 1 bottom fan mount go for it, it looks like the PWM hub in the case can handle it. But I dont know if you'll really see much in the way of better cooling with that many fans.