Hi guys, Just out of curiosity (I don't plan to buy anything soon as such), I wanted to know certain things about stacks... Here are a few queries.. 1 - Do amp heads have speakers? Do they work by themselves? 2 - Do all amp heads have tubes or are there solid state heads too? 3 - Do the cabinets have tubes in them too? 4 - Is it necessary to always have cabs of higher wattage than the head?