It's very probable that none of these offerings will work well if your application integration is not aware of itself as a group of applications and services.

Think about it: Install Apache on one host. OK. Now, two hosts... Well, do you round robin DNS, or do you run a squid reverse proxy, do you buy something else...

Next, how are you going to monitor this monster, Nagios or OpenView... or something else.

How many people are responsible for this puppy?

Oh, yeah... And I'm just talking about static web hosting, you start having all kinds of fun when you want to track user sessions, etc.

My advice to you is to look into an Application Service Provider. Make them do all of the integration work.

If you can afford Internet connectivity to a pair of servers, you can probably afford an Application Service Provider.