Hi!
Well the speakers seem so much better. I mean you get a 5.1 decent quality sound dirt cheap. I'm not sure about reliability or quality since the price is low but if AJ says it's good I have no doubt about it. The only thing i'm not clear on is whether this setup is self powered or it requires an additional amplifier. Wil have to wait for AJ to reply.

In regards to you needing a mixer or not it's not a requirement at this point since you only have one KB right now. If you add more in the future then you will require a mixer. Right now a mixer will only give you some more gain, a fatter sound and some EQ to mess with. If it is a decent mixer of coarse. Some cheap stuff just messes things up.

KB Amp doesn't seem bad at all since it's kind of an "All in one" unit optimized for live gigs. However the main downside is lack of stereo since it only sports one speaker. Also, it leaves little room for expansion because it only has one stereo input. In overall it limits you to just a mono sound. Okay for guitars but sucks for synths. It's not like the 70's or early 80's when KBs only had a mono out. Nowadays things are in stereo and things mainly sound good in stereo. You can get away with mono but as a keyboard player you deserve way way better than that.

-ED-