The performance of BigFix/TEM/IEM is often limited more by Disk speed than anything else. The other major consideration is configuration and structure of your infrastructure.
I definitely recommend either SSDs in RAID1 or PCI-E SSDs with frequent backups for the DB and FillDB. See this: FillDB Buffer Size Issue
- Are the 6 tier 1 relays running on server class hardware with fast NICs?
- Are the 3000 tier 2 relays all on at least Gigabit? Are they user workstations?
- How is the performance now? Is it satisfactory?
- How many clients to you anticipate adding?
- Are you using Message Level Encryption?
- How many simultaneous console operators do you have / plan to have?
- How many simultaneous web reports users do you have / plan to have?
- How many open actions do you have?
- How many open baselines do you have?
- How many components per baseline on average?