Pound for pound ... the psr2000 will give you the most for your money. The Casio is a dead horse that will have NO third party support in the future, the Roland is nice, but dated and no vocal inputs, so that leaves the Yamaha. The keypad is flimsy, so be careful, but lots of guys are using them every week with no problems. It's a great bargain for what you pay/what you get.

If you're not going to use the vocal section .... maybe there are better choices, but as far as what you told us ..... I'd recommend the 2k.