The fan speed contributes to the noise because of 2 things first more air is being moved and you can hear it moving (turbulance) the second thing is the faster the fan is spinning the more noise it makes from its bearings.
Good quality fans have better bearings and so are quieter at higher speeds however you do not eliminate the turbulance noise.
What Pob meant about vent noise is that the added turbulence generated from the mesh or grill can make more noise than you may expect.
One other thing you can try is to get vibration dampers to mount the fans but these often come with the better fans and having better quaility fans will make significantly more difference than any silicon mounts.
The fan that you took a picture of has a 4 pin (molex) connection if you get a fan controller you will need to replace the fans as well as most if not all fan controllers use a 3 pin fan connector (or 4 pin PWM)
If you want a nice quiet case then a fan controller and some new fans may be in order, Yate Loon D12SL
http://www.chilledpc.co.uk/shop/prod...products_id=48 £4 each plus a fan controller, so about £50 for the lot. You could get away with less fans couple on the top and one on the front will probably be sufficient.
As to the wiring you should be able to route the main power cables up behind the motherboard tray and come out of the holes to the right of the motherboard, eqaully you could route some of the other cables this way as well.