Hello Angelo,
Not the original amp or speakers as yet but a pair of Behringer Studio 50 monitors. Surprisingly these sound better to my ear when mounted inside the cabinet!
I've kept the original 12" woofer, two 8" midrange, and tiny tweeter to add with an amp later......maybe.
Don't be put off having a go at the project, it's simply a matter of stripping out the old electronics which leaves a flat tray, and possibly adding a small inside shelf for the speakers.
Although the photos show a tilted screen on the SX it's not necessary and I've now changed this back to original and tilted the keyboard instead.
My hope initially was to include the Keystation 61 within the cabinet and did try extending the roll-top rails out the back, but the mod destroyed the profile of the U60. Just adding a couple of swing arms in front is much simpler and it takes less than a minute to add or remove the auxilliary board.
Robert.