"SX900 has the Motif key-bed without the After Touch. We are waiting for a report from Frank at Audio Works in the USA about the key bed. He would know about the differences since he sells a lot of Yamaha keyboards."
Joe H Psr Tutorial Forum

I have the Motif XF, and I really like the keys. They're called, FSX. If the SX900 has the same keys, it's a major step up from the PSR-975 and previous models.

There's a guy on the PSR Tutorial forum who said the keys on the SX900 felt like those of a Tyros 2. I've never seen a T2 before so whatever that felt like could possibly be the initial benchmark.

I have a T-2 and going to lighter board with same key bed and 3 right hand sounds and speakers sound like easy decision. Should be able to load all my existing settings right in. The key feel definitely better than 950 I had. Smoother, and no fatigue noticed.

Spoiled by my tilt screen though..

My reading of the SX900 information on that it is a more heavily weighted version of the previous PSR keybed and not the FSX.

T2 is FSX I think.

Based on the PSR-S series, both models have been completely redesigned and come with a wide array of exciting new features for even more playing, composition and songwriting possibilities.

Visually, the stylish and intriguing PSR-SX700 stands out with its clear lines and dynamic form. Designed to offer a maximum of playing enjoyment, the PSR-SX700 comes equipped with a broad palette of features and functions for more musical inspiration and creative exploration. The new FSB keyboard, complete with 61 keys offers players remarkable comfort and nuanced expression, thanks to its heavier initial key resistance and greater key travel. The new joystick provides players with greater intuitive pitch and modulation control for more sound variability.

At the technological heart of the PSR-SX700 is the newly designed graphic user interface complete with an integrated 7.0-inch touch screen display which offers the maximum of user-friendly functionality. As for sound, the PSR-SX700 possesses a comprehensive and sonically stunning set of 1,507 high-quality authentic voices and 400 styles for unlimited musical combinations. All functions can now be activated even faster using the new assignable buttons, making each function instantly recallable with a single touch.

In terms of memory, the PSR-SX comes equipped with 1 GB user memory and further 400 MB expansion memory for Voice & Style Expansion. In addition to WAV recording, MP3 recording is also available, as well and audio files which can be both played via USB-to-device and user memory.

Created with the same dynamic style, the PSR-SX900 offers even more features for professional composition and performances. This includes a total of 1,873 voices, 525 styles for greater musical choice, as well as new drum kits (derived from the Revo! Drums of Genos) that add greater authenticity to every composition and performance. An additional Chord Looper function allows to record and playback chord sequences, freeing your left hand from playing, while the new expansive sound field Speaker, Bluetooth® audio and high-resolution sound for line out, sub-outs enhance every performance. Moreover, the PSR-SX comes with 4 GB user memory and further 1 GB expansion memory for Voice & Style Expansion.