I just got a Fender Rumble 500 combo amp. I like the amp and I am thinking about getting the 210 extension cab for it. I also have an oppurtunity to purchase a second used Fender Rumble 500 combo for not much more than the new 210 extension cab would be. My question is , If I ran two Fender Rumble 500 combo amps together using the effects send/return to ‘slave’ one of the combos, would this give me more volume than adding the 210 extension cab to one combo would? In theory the two combo’s would push 350 watts each into 2 10” speakers giving you a total of 700 watts into 4 10’s. Using the extension cab would give you 500 watts into 4 10’s.