Two ISPs on the same interface

[Papo Napolitano]

Hello all,

I got two ISP lines (1 Mb and 6 Mb) and was planning to route outgoing 
"guest traffic" thru the smaller one.
Problem is my FW only has two NICs.
If both external routers are connected to a Cisco switch as well as the 
external OpenBSD interface, is it possible to use route-to to send 
packets to the ISP gateway I choose?
All the examples I found use three NICs.
Thanks.-