Dude, you've got it all wrong
Static pages (since you're going to host the mysql database on another machine, i assume the frontent machine will only be used for static content) can be served at 10mbps from a simple celeron machine.
Lots of database queries on the other hand could use a Dual Xeon to speed things up a lot. A celeron will start lagging as soon as you're going to send alot of queries to the mysqld.
My opinion: Either do it the other way around (Dual Xeon for db, Celly for static), or buy another Dual Xeon. Some extra firepower at the front won't hurt either.