Hi:

I had and X1 HD and then when it came out around 5 years ago, the SD1, then another SD1, I became a product specialist on those boards, their sounds and styles are incredible, Aldo, for some taste, the styles are "in your face" type, but I did like them, their user interface is a little more complex that other keyboards, but when you "get it", is easy, just like with Korgs, or other boards, the SD1 I will assume that is due for a replacement SOON, in few months, a smaller model, the SD5 (61 Keys and speakers built in) and with new features like Riff, after fill an others....is coming out with an updated sound generation. The SD1/SD1 Plus for MY style of playing, the 64 note polyphony was an issue, that is why I change it for the Yamaha Tyros2 that has 128. By the way, the new SD5 has also 128 note polyphony.
Both units(SD1/T2) are great, depending of your playing style, in the SD1 still has a few sounds that are better to MY ears than the T2, example, the human choirs....the MMMMHHHs, the TOO TOO, the AAAHHH, is real, the DOOuuuappp !!....there are other sound that by now are a little dated.
Can you expand more if you are going to be playing styles or midi files or are you considering to use it with a MIDI controller?, the reason I ask is because the SD1 works great with accordions, midi guitars, etc...Here in the Valley area, there a a lot of performers using this set ups. I see that the T2 has already those configurations, but I have not seen/heard it yet in action with a controller that type. The T2 has one of the BEST user friendly interfaces.