Sorry, I'm confused; need more info. Do you already have a 210XST(8) or 210XST(4) and looking to add to it???
If you are doing small clubs (not sure what you consider small clubs and do you run DI to FOH???) and weddings and would NEVER want to utilize multiple Cabs; get the 210XST(4) and be done. Problem I have with this? The 800B is way too much amp for one 210XST(4 or 8 Ohm) Cab. Or,
IF I were going to run just one Cab with the 800B (btw: not a chance), I'd get the 410XLT(4). Otherwise, I'm running the 210XST(8) and 410XLT(8) Bridged.
If you are going to just play small clubs and already have a 210XST(8), add a 210XLT(8) and call it a day. This way you will have the option of running one or both Cabs bridged and have tone and headroom to spare. Plus, you have portability options.
