Piano Amplification?

I have a Yamaha YPG-635 and the speakers aren't loud enough to jam with other instruments. What is a good, cheap amplifier to get? I want it to be loud enough to cut through drums, guitars, etc.

Also, what is the difference between an amp and a monitor? Which one is better to get?

Also, it seems that the mid/high keys don't have the same sustain as the bass notes. It's like I strike them and the decay is too much...if that makes sense. I want them to have the same opacity as an acoustic piano. Do I need to get an Equalizer or a compresser or something?

thanks!

JBL Eon powered 15" Pa speaker would be good choice. The 300 watt ones sold for around $350 each new. If you want stereo but a single 15 with tweeter is enough air movement, then pair of thbe JBL Eon 10" would be good choice. Alternately for great hifi sound a Eden Nemesis 15" combo with its comp tweeter would be good or pair of their 12" combos. They make a 10" combo but its power may not be enough with a pair. Genz Benz also makes great bass combos which like the Eden nemesis series outperform most keyboard combos sound wise imo. Genz Benz does also make keybaord combo (bass combo with extra inputs). For those on tight budget, Peavey and Acoustic are good choices.

sweet! I'll look into those.

I've heard of some key players using bass amps before (Sigur Ros)...is a bass amp better than a regular one? what are the pros/cons?