Hi Steve,
yes BIAB is software. I gather it's not really the way you want to go, but it might be worth 10 minutes of your time just to check out some of the demo's.
http://www.pgmusic.com/bbwin.demos.htm

I luv my arrangers because I enjoy playing them & I enjoy fiddling round with the styles.

On the other hand if all I wanted to do was create backing tracks or record songs, I could have saved myself ( or should I say, saved my husband) $1,000's of dollars on my arranger keyboards in the last 3 or 4 years keyboards.

Prior to the real tracks , I wouldn't have considered BIAB as an alternative, I was never really that happy with their midi styles. Some were good ,some mediocre, some really bad.

Also depends on the genre of music you like, BIAB is big on Jazz,Rock/Pop & Country. They also have midi classical & soundtrack which I enjoy.

Korg PA800 doesn't have a great deal in the way of country, it has some, but members used to complain there wasn't enough.

So really be worthwhile if you are interested in an arranger to not only make sure it has the sequencing functions you require, but that it also has the type of styles you require.