Absolutely, for example when I added the VC/WC above the FB it added 28 square feet of rack space. Also have you ever tried to put aluminum pans in a round CC? I can put 2 full sized pans in each shelf above the FB. The doors swing instead of lift, so anyone can open the door. The heat/smoke that goes into the VC doesn't even go into the calculation for the rest of the cooker so it is sorta like being free. The fire basket is better in the square FB too, because now I can have a ash pan under it for easy cleaning and no mess. If you go square doors on the tank too, you will have easy open doors without counter weights.
Current Smokers: Backyard RF Offset and Hybrid RF Offset trailer rig with Cowboy cooker and fish fryer, always room for more........
In my opinion the insulated fire box kind of depends on your climate unless you just want an insulated FB. If it's real cold where you plan on using it then I would insulate but if it isn't cold I would use the thickest metal available.