Here is a URL for a lightweight hard case for the PSR-s900:
http://www.midi-store.com/Guardian-Featherweight-keyboard-case-p-16494.html

It won't fit in the trunk of my car so I am sticking with the Kaces 9kb:
http://www.kraftmusic.com/catalog/accessories/index.asp?product=1219

If you use the kaces, make sure you put a piece of foam on top of your keyboard so that you don't damage your LCD. I did this once with my PSR740.

I also use this stretchable Gator cover to avoid scratches and so that pieces of foam don't get into the keyboard:
http://www.amazon.com/GKC1540-61-Key-Keyboard-Cover/dp/B0002CZTIE

Beakybird

Also check out what I just got for my PA800: www.gigskinz.com
GSK6 - 61 key bag
44 x 16.25 x 5.5
The PA800 is snug as in a glove ! That's the way I like it - and there are inline skate wheels, 3 pockets, and great stiff protection. No foam needed !

I am using one with my G70..

Im using one for my accessories, cables & wires.

that looks too small for the PSR-S900:

Width 1,003mm (39-5/8")
Depth 433mm (17-1/8")
Height 148mm (5-7/8")

The gigskinz is 44x16 1/4x 5 1/2

Beakybird

i use a gig skin with my s900

fits good, a little snug but well protected

mikey

The Kaces 9kb dimensions are:

44.5" x 17" x 6.5," closer to the Width 1,003mm (39-5/8")x (17-1/8")x (5-7/8") of the PSR-S900. There's room for the music rest, accessories, sheet music, power cord.

I put the mic cable, a/c adapter, and headset in a tupperware right next to the keyboard and all the other stuff on top of the slice of foam, and it fits as snug as a bug. The buttons and LCD are very well protected because they are covered not only by foam, but by the other stuff.

As everything goes on my dolly, I don't need inline wheels on my gig bag. Even though I suppose that they would be convenient for just rolling the keyboard a couple of feet.

Beakybird

Also, my large Giga Skinz bag[for my G70]..only weighs 13 pounds, compared to my same size Gator bag with wheels..26 pounds..

To Beaky Bird,
I just bought a psr-s900, and am loving it. The case that you mentioned at the top of the page (the Guardian Featherweight 61 keys), Before I buy one, Are you a hundred percent sure that it fits the s900? No problems? (I'll need to take it on a plane a few times).

P.S. I'm happy that I didn't get the Tyros2, I don't see it worthy worthy enough to cost the extra $1800 or so! Thanks for the suggestion.

I'm positive the Guardian 61 key case is suitable for the PSR-S900. It's a good fit. A little bit of space leftover lengthwise, about 4". Depth is perfect. Height has maybe 1 inch of wiggle room. Case comes with pads that you can use to stop keyboard from sliding around.

Beakybird