Suggestions for network design

Looking for some suggestions on how to redesign our network.

Currently we have 2x wan connections:-
- 4/4M fibre (ethernet port) used for web / email servers, trixbox voip, vpn
- 20000/1024Kbps aDSL used for general web surfing by users

Currently they each go to their own firewall/routers then onto our LAN. The DSL connection router has an untangle box in between it and the lan to provide filtering/blocking to the users.

I am considering putting on another aDSL connection to give our users more speed too.

So initially wondering if I should get a router to connect all 3 WAN connections into or keep the server side stuff separate from the user web traffic? Having it all in one would be nice for management I guess.

Hoping to find some device which isn't over complex to setup so that we can continue to setup in house rather than requiring vendor specific knowledge. Should allow us to dedicate a portion of bandwidth on the fibre to voip only.

Currently using snapgear/cyberguard/securecomputing and now known as mcafee linux based UTM devices, SG580 and SG560. Also have HP procurve L2 switches.
We are a small business with 40ish staff.