I've had a single custom road case that has fit my G70, G1000 and K2500 (specifically built to fit the Roland lengthwise, and the Kurzweil depth-wise) for about 15 years or so...

Mind you, it probably weighs more than your PSR3K! But my gear looks mint, the case still looks mint, and it has gone through a 90-mph car wreck without any damage to the contents (my G70). I figure that made it worth the weight all these years, alone..!

There's a false economy in buying ultra-lightweight anything, especially if you expect it to work worry free for decades...