Why do you want to run clusters anyhow? In my option they aren't worth the complication. Can you remember that each switch has a different IP? Good, now there you go, you don't need clustering.
If you are already using switches there isn't a way to reduce collisions except maybe moving to full duplex. Collisions are normal in ethernet and, unless they're high, nothing to worry about. To reduce the broadcasts you really need more VLANS. If you're being flooded you can reduce them with the broadcast command.
-Jeff ----------------------------------------
Wassabi Pop Tarts! Write Kellogs today!