Dedicated reporting server?...

I am seeking advice. Consider: Distributed data warehouse, consisting of multiple dimensional marts, on multiple servers, Windows, MS SQL, Cisco net.
The largest mart is 300 GB, the smallest is 50 GB. Nightly ETL (Informatica), the availability SLA is 12x5, but it's more like 16x7.

Introducing SSRS/SSAS. There will be multiple "dashboards", with multiple reports, ROLAP and MOLAP cubes, etc.
Assuming these dashboards and cubes will be using/relying upon the data from multiple marts, do I build a dedicated "reporting" server to carry these dashboards and cubes, or do I deploy the dashboards on the same servers that the marts are on? I am leaning more toward the dedicate SSRS reporting server, but am far from certain I am doing the right thing.

What does everyone think?