A great keyboard is only as good as its amplification...even a Yamaha Motif XS will sound poorly through a low budget amplifier. You are buying a top of the line keyboard, get a top of the line amplifier!
This is true - I think "Behringer" stands for "Bottom of the Barrel" in German...
They take other manufacturers' product designs and copy them & sell the resulting knockoff for much less money. Though some have bought & used Behringer products (they make everything - amps, PA, mics., recording equipment...) w/satisfaction, many have found that they're unreliable crap that will eventually fail sooner if not later.
If the band you're playing in can put you (your keys) thru the PA you're much better off - then you can either monitor yourself on stage w/a PA monitor or get your own keyboard amp - the Roland KC150 is a good unit to try:
http://www.americanmusical.com/Item--i-ROL-KC150-LIST
...or move up to it's bigger brothers the KC350 or KC550 for more power (but more money, of course) -
http://www.americanmusical.com/Item--i-ROL-KC350-LIST
http://www.americanmusical.com/Item--i-ROL-KC550-LIST
I bought a pair of JBL EON15 G2's about 7 yrs. ago -
http://www.americanmusical.com/Item--i-JBL-EON15G2-PAK-LIST
...which I used as PA mains and sometimes would use one as a stage monitor when someone else brought the PA.
Two years ago I moved to the Motion Sound KP200S -
http://www.americanmusical.com/Item--i-MOI-KP200S-LIST - which is a pricey but really sweet-sound amp, though a little bit underpowered. If you're playing in a loud rock band I'd go for a JBL EON15 G2 as your stage monitor. I still have the EONs for the occasional gigs where I have to supply PA.
