If you are going to want to send the drums over to BFD or EZ Drummer, or something like that, then the arranger HAS to send MIDI for the drums, not simple one note triggers of a loop...
The thing is, you are STILL looking for inspiration while you are making the 'mock up', so you want an arranger with great styles, but, OTOH, you want to replace almost everything anyway, so it HAS to be MIDI for all the parts. The Audya's drums, bass and guitar audio loops will either have to be used 'as is' or you will have to play them by hand completely, as there is no MIDI out of an audio track.
I think you MIGHT want to consider perhaps a PA800 to save yourself money... you probably already got an 88 or 76 in the studio, yes? So you can MIDI that to the arranger for an expanded keybed, and the rest of the PA800's capabilities are almost identical to the PA2Xpro, other than sample RAM (and you'll be using VSTi's for that).
Plus the PA800 has speakers, so it's a piece of cake to take it home, or to a different room in the studio, and work on a song while other stuff goes on in the main tracking room, or over to a friend and collaborator's (or the artist's) house for a writing session with no need for a sound system.
Just curious, though, why you think the T2 is getting long in the tooth...? Is it a MIDI issue, or are you getting bored with the styles (lot's of Korg conversions available)? If you are replacing almost everything, one would think that the source arranger doesn't really matter all that much... just the styles that it plays.
_________________________
An arranger is just a tool. What matters is what you build with it..!