I would stick with 6 beams if you are on 120 Weapons Power or so.
Maybe the Assault Cruiser and Excel could get some use from the DBB or extra Torp tube, but the Oddy with its crawling turn rate will have a hard time bringing that weapons to bear after the initial 5 seconds forward charge.
My current setup (PvE wise) is 6 beams, with a Cluster Torpedo fore and a Tricobalt mine aft. After many different configurations this is probably what works best for my playstyle. As I'm usually on broadsides, the long recharge timers on Cluster Torp and Tricobalts are not an issue, as faster firing weapons like Photon/Quantum torps would waste firing cycles while enemies are on my side.
Photon/Quantum mines works nice though, as you dont need to point your nose/back to the target for them to work (at least if like to play close and personal to targets, that's it )...