Hello Channelzer0,
You could set this up in a couple of different ways. One of the more simple ways would be to use two switches, you connect one ISP to each switch and run two ethernet connections from each ISP switch to each Balance. Between the firewall and the Balances setup another switch and connect each Balance to this switch, and than the switch to the firewall. A diagram of this deployment can be found in this post here.
You could get away with one switch between the ISPs by configuring some of the ports to be access ports.