Depending on the size of your lens, just a 30L would be enough, that of course mean you don't have a 300mm or 500mm prime going in there. Difference between a cabinet and a box? cabinet runs on electricity and is more convenient, dry box uses silica gel or other drying agents of your choice.
30 litre should be just nice for 2 bodies & 4 lens. Im using a 30 litre that holds a 500D, 5D2, 18-55,24-70,10-22 and 50f1.8 + some filters. Abit pack if you are not the kind who is gentle as you may knock other items when taking in or out.
buy a bigger capacity and suffer the bbb virus. haaa