Sounds like you have a good plan so far. As far as app server I am partial to open souce (jboss) but that is at least partially because the company I have been working for the last few years is to cheap to consider anything else. We have pushed 80,000+ users/day through very server CPU intensive promotional websites running jboss on a few cheap Intel boxen with no major issues using the Apache -> Tomcat/JBoss -> Oracle 8 combo.

We did run ATG's Dynamo for a couple of years (avoid it like the plaque) and evaluated Oracle's app server (too big, too weird, to unfinished feeling) as part of their reporting suite. I have never used weblogic personally, but have heard enough good things that I would consider it if I was looking for a new app server.

-Mike