Dual WAN address router

We have just set up a Sharepoint client access site. Because we wanted our
clients to access it with a different URL, we got a 2nd public IP address
from our ISP (old: x.x.45.146/22 plus new: x.x.143.10/22). Their premises
equipment is straight pass-thru and delivering both addresses to one LAN side
ehternet port.

We are looking for a good quality router that can be set up with these 2
static ip addresses on the WAN port and NAT each one to separate addresses on
the LAN side (i.e. x.x.45.146 -> 192.168.16.10 and x.x.143.10:3150 ->
192.168.16.11:3160).

Can anyone suggest what is the best router for the least $ (cost is a
factor)? I'm leaning toward Cisco because I'm pretty decent with IOS, but
dual WAN IP capability is not an easy spec to find when comparing devices
(there are a number of devices with 2 physically separate WAN ports, but this
in not what we need).

We're also looking at Sonicwall and Fortinet.

All help is greatly appreciated!