i take it i'd need a second IP ? don't know what the charge is yet...
You don't need a second IP unless you have a need to have 2 external facing computers (most users do not have this need and you lose you hardware firewall in the router)
The router would handle everything, the router faces the internet and distributes traffic to internal computers.
1 router can handle a lot of computers.
For cheap router you do get what you pay for but I have had good experience with Trend and Asus.
Belkin is good but I found it lacking in options to configure.
Of course you have the big names Linksys/Cisco and Dlink who have offerings accross all prices.
really it all depends on what features you want and what you plan to do.