Hi
do revert back whats the ip addressing scheme in place out there in all the routers (cisco and 2 non cisco).
In you cisco router you can point the 2 static default routes towards the non cisco gears which can take care of your outgoing traffic from your local lan but the incoming traffic from the outside via the non cisco gears has to be routed properly..
Whats the local NAT scenario being deployed ? and also information is reqd on the local LAN address space to help u out....
regds