Do you know the specs of the Linksys? Is it an 802.11g router? Is it a WRT45G (It should say on the front of the router, in very small letters)? Are the macs you are getting all "brand new" macs, no second hand macs?
The Mac Pro you are getting, great choice by the way, is coming right from Apple? How old is your wife's MacBook Pro?
The reason I ask these questions is that if these macs you are getting are only a few months old, then an Airport Extreme might be beneficial because all the new macs support the 802.11n Draft. The New Airport Extreme Base Station is also n draft supported. So if you are going to be sending files within your network (NOT the internet), you can get up to 1000 MB / sec. But, remember, all the Macs must be a few months old or newer to support the n Draft.
I hope this helps somewhat.
Cheerio
Searay