George, I can only answer on the PR604, since it's one I've used on occasion. There isn't much I can say to encourage you to buy one of these units if you are going to get into arranging and composing music. They are great sounding standup units, but tough to carry around and certainly don't have the features of a KN6000-7000. It all depends on what you want to do with the thing, I suppose. The KN keyboards have the PR's beat all to pieces when it come to playing functions, sounds, rhythms, etc. You can listen to the sequenced songs and styles from the KN keyboards, but you can't do anything else with them. I don't think the composers are compatible with each other and I also think the versatility of the KN's far outshines the PR's. They just aren't in the same league, and the price difference isn't that great, either. I would highly recommend the new KN7000 if you are into something more than playing music. Composing, arranging and recording music is much enhanced with the KN series. In my opinion, anyway. Hope this helps, and welcome to the forum. Even if you do end up buying a PR, you'll still find things of interest here.