The thing that occurs to me is, why do you want to avoid the easiest, most cost effective, most powerful way to record and compose music available today?

The computer.

Even the most sophisticated workstations, let alone the latest greatest arrangers, come a VERY distant second to the power, ease of use and quality of sounds available to computer users.

Sure, you need an arranger in the first place to perhaps speed up the initial composing and comping process, but trying to shoehorn the entire process into one keyboard is, IMO, unnecessarily cramping your style, limiting your options, and putting a self-imposed limit on how good the sounds you use are...

There is no comparison between the better VSTi's and keyboard sounds nowadays. No matter HOW good the arranger sounds, there's a VSTi (often at a cost of a 20th of the arranger, even less when you consider a $5000 Tyros!). There is no comparison between the ease and power of recording audio and manipulating it on a nice 27" screen rather than a tiny 4" window, nor does any arranger have as high quality a suite of effects for any conceivable need.

Personally, I would recommend the least expensive arranger you can get away with, in fact, maybe stick with the PA1X you already have. It's enough to quickly record a MIDI rough of the tune (plenty of PA3X to PA1x style conversions out there, plus a ton of other manufacturer styles have been converted). But combine this with a computer, a nice DAW, and a suite of VSTi's and a loop library, and you can make music no one arranger ever will...

Is there any particular reason other than technophobia that is preventing you wanting to use the BEST tool for the job?