Many companies, including Roland, Hartke, Peavey, Traynor, Crate and Behringer, make affordable, mid-priced keyboard amps that'll cost you less than $300. Even at this price, these amps are utilitarian, able to handle instruments at both ends of the frequency spectrum. The 180-watt, 4-channel Stereo Roland KC-550 and Hartke's 200-watt, 4-channel KM200 are only two popular selections in this category.
Basically self-contained, compact sound systems, amps like the ones in Roland's KB series work for voice, keyboards, acoustic and electric guitar, drum machines and backing machines. Other amps that do double duty as PA systems and keyboard amps are the 180-watt, 4-channel Behringer K1800FX and Yamaha's 10-channel, 500-watt StagePas 500. Peavey's 150-watt, 5-channel KB5 is also touted as a "personal PA system in a keyboard amp." Many keyboard players take the leap and plug into PA systems that don't even pretend to be keyboard amps, like the JBL's powered EON speakers.
Motion Sounds and Barbetta are generally considered a cut above, not only in price but in sound. Motion Sounds are usually priced between $750 and $1,700 (as of 2010), and some of the cabinets have a rotary speaker that invokes the famous Leslie sound. Barbetta's amps, including the 225-watt SONA 31C Keyboard Combo Amplifier, receive high marks for clarity and portability.
The least expensive, compact version of Bose's L1 system and the matching T1 ToneMatch audio engine will set you back about $1,000, but those who've tried it swear by its clear sound and easy portability. It features six small drivers mounted at precise angles inside a slim, vertical enclosure, and the system's interlocking components make it easy to transport, set up and break down. The entire system, with loudspeaker, power stand and extensions, weighs 29 lbs.