I have the BG250 and Randombass is correct, there is no ext speaker out as the internal one is rated at 250 watts at 4 ohms, so in theory you are getting all the amps power. I have gigged it several times and it kept up with a 100 watt guitar amp and noisy drummer. It does seem a tad delicate though. The push buttons are a bit wobbly and the pvc covering on the cab doesnt seem very robust.
But it sounds ok, is loud enough for my needs, is very light and I use the headphone and aux in function for all my home practice, which keeps the wife and neighbours happy.