That case will not be a quiet case. Your plan to add sound dampening is a waste in that design. With all the side fans it will cool well but will be a rather loud rig.
Your suggested build will OC well but if you want quiet you need to go with a different case.
I agree with Rolli that you should not pay for a OC'd kit, do the OC'ing yourself through the UEFI.
You should also not pay for factory OC on the GPU, use reference clocked cards and OC them yourself with MSI Afterburner. Just buy GPU cards with good cooling like ASUS, MSI or Gigabyte multiple fan cards. You can OC the EVGA doubleshot GTX570 to 800 MHz (and beyond) easily. I run my reference PNY GTX 470 at 800 MHz.
Nice build, but you should not pay extra for the OC-ing that you should control yourself.