This is pretty good advice from someone that has an S910...!

I guess a lot depends on whether you do much sequencing, and replacement of the S910's sounds already, or you tend to want it easy, and everything come out of one machine, ready to go. If the latter, then the step up to the T4 is probably a good bet.

But, in all fairness, most TOTL WS's are more capable than their 'home keyboard' siblings, with fancy groove, loop and arp capabilities, usually MUCH more capable and flexible samplers, master keyboard capabilities and DAW control possibilities (sliders for track control, transport buttons, etc.) and, on the whole, better, more punchy sounds. Especially in the case of the Kronos, you get 12GB (!) of samples, ready to go. That's more than any loaded up arranger, by a factor of at least six (and more like 15 )!

And, the sad thing is, even the Kronos is likely to be less expensive than the T4. A Kronos 88, at that! The 61 will definitely be less expensive!

Another WS to take a good hard look at would be the Yamaha MotifXF. Over twice as much flash RAM as the T4, and a software KARMA module is available, if you like that. Plus full audio loop and arp capabilities, and some seriously punchy sounds.

I don't know if, at the moment, you are using the S910 solely, in the studio, or whether you already use it for the initial ideas, then flesh it out with sequencing, editing and replacement, but if you do, give the Kronos or MoXF a serious look. If you want to just get 'close enough' and do it all in the arranger, then maybe the T4 is worth the money. But that's a WHOLE chunk of change to do something that your S910 already gets 80% there as is...