I own a sunn 300t and am in the market for a new cab. I am leaning towards the 900w Lab Systems 6x10 (i live in Australia) as this falls within my budget, is competitively priced and is an aussie product with a good reputation. My question is regarding the resistance, as on the website it says that the nominal impedance of the cab is 5.3ohms. My sunn has a switch between 2,4,or8 ohms. I'm assuming that i would set the head at 4 ohms but I wanted to make sure that this would in no way cause the tubes or transformers any stress that could damage it. I know that ohmage is not a static thing but I just want some affirmation from those who are a bit more tech-savvy than myself. I also would like some advice if I decide to go with a 4x10 & 1x15 or similar setup. Would I be best to choose 2 X 4ohm cabs and run the sunn @ 2ohms, or choose 2 X 8 ohm cabs and run the sunn @ 4ohm load? My concern is more associated running the head at its most efficient and reliable (rather than sound quality and volume levels, as I assume there would be little difference here). For example - will the tubes/transformers work harder @ 2ohms than 4ohms. etc? PS. This is my first post - its good to be a member!