George is right about the 550's sequencer.. I can speak from experience on that one.. I own the PSR-550.. It has pretty good sounds on it, but if you're going to record it's much easier on the PSR-1000 and up because they have internal sequencers.. The 550 uses the disk drive.. There are numerous menus to go through just to record one track. I too am a guitar player, and in Febuary I will be upgrading to either a PSR-1000 or 1100 for several reasons and that's because the 1000 and up have internal sequencers, 4 variations per style with numerous intros and endings, fade in and out, allows basic voice editing, better sound quality, way better speakers (the 550's speakers are just plain terrible my friend, and the tweeters don't even work.. they're just for show), L&R output jacks (the 550 uses the one jack for the headphone and output, and is very noisy when recording to external gear) George is right... If you're a guitar player go with the 1000 and up. Even though I've been playing the keys for over 20 years, I have also been a guitar player for many years as well. You'll find that the 550 will fall short when used to create full compositions when playing along with a guitar. You might even want to consider a used PSR-740... I know Travlin'easy was selling one or two not too long ago. The only downside is that the 740 has the same sequencer as the 550, but it has drawbars, 12mbs of sound, vocalizer, 4 variations per style, modulation wheel, same watt power on speakers, but the 740 has much better quality of speakers and the tweeters work...
... It would work well for a guitar player, but when it comes to the sequencer that falls down to personal taste.. That's why I'm going with either the 1000 or 1100.
Squeak