Depending on your companies IT budget.
It is advise to host a single application or service individually on servers rather than hosting multiple services from a single server.
Well server performance compared to previous years when Dual CPUs was great during the older days. Now servers come with 8-16 CPUs cores because of higher applications requirements and the ability to run multiple operating systems using Vmware, Citrix and MS Hyper V.
By hosting a single service for a single server would be wasteful of resources. Even Microsoft Small Business have the multiple services all in one server. (See versions here)
You must also ensure that there are backups or fail-over solutions for hosting multiple applications.
The management needs to measure their ROI for the systems downtime. This is to ensure the daily business functions downtime they can afford.