Thanks Bill, that is a very interesting view and of course you're not the only one that has suggested that the T2 sounded more sweeter / softer than the T3.

I have been very happy with the T3 that's because I am comparing it to the previous keyboard I used (PA1x), I still have this but I prefer the T3.

I assumed the T4 was the T3 with knobs on, however, now it's being suggested that the entire sound system is better which is a different kettle of fish, we are then talking about a completely new keyboard and not an upgrade.

I do need to hear it side by side really, that's the only option left unless I just buy it anyway.