I would not purchase a 76 key Tyros2. Why, because I don't like 61 key version. It has nothing to do with looks, build quality, Navigation (OS), or number of keys. I just don't like the sound of the styles. I assure you, I would choose a 61 key PA800 over a 76 key Tyros. This assumes that their current approach to styles is carried over to the 76 key model. However, I don't consider my answer valid as I don't/won't use an arranger outside of the studio so my needs are different from a pro OMB.
As I've said many times before, I'd be happiest if all the manufacturers made their TOTL arranger in module format and provided a software template for some standardized super-controller which was available in 61, 76, or 88 key format, with or without built-in speakers. Better yet, just a circuit board that would be hosted by something like Reaktor? or some non-specific (also standardized) hosting 'box'. Of course, this makes way too much sense and as such, will never come to fruition.
"Faith means not wanting to know what is true." [Nietzsche]