NETGEAR SRX5308 best end user experience, on the web

We have a small company with under twenty five users, in Sweden. The network looks like in this PDF (http://www.smartlogon.se/diagram1.pdf). Because of that we have problem with bandwidth there the company is located, we need to take every opportunity to explore wearies technologies. We are using a SRX5308 Firmware version 4.2.0-22 as router/firewall, it was first chosen because of the possibility to rout be twin deferent production networks with hi throughput, and redundancy of WAN connection.

WAN 1 shell be used of end user for browsing the net, video streaming and other end user things.

WAN 3 is used for primary MX, SharePoint, MSVPN, communication with customers systems, security systems like an alarm and DirectAccess

WAN 4 are used for secondary MX, alarm and CCTV.

The problem is end users experience. When you jumps on your Internet browser ones get 50 Mb and the next time it is 512Kb, it makes one think suicide is a solution you gets crazy.

Then I try to force the traffic to go through WAN 1, the other WAN connections is going down and can’t be accessed from the internet.

How can I give the end users 50 Mb every time, then they hits the Internet??