Lukitoh,
If you have the choice of the PSR-550 or the PSR-740 take the 740.. It is by far a better keyboard.. Great sound quality, really good speakers and the tweeters really ad crispness to the sound. Better screen, modulation wheel, EQ, drawbars, 4 variations per style, nicer look, better build quality, vocalizer, geez I could go on and on.... The 740 is a nice keyboard and would out perform the 550 any day...

Squeak