Thanks for filling me in m8.
You wont go wrong with either arranger what you mentioned then. The Tyros 2 displays the lyrics on screen and they are easy to view. The Solton displays lyrics as well, but my own personal preference out of those 2 for midi file playback would be the Tyros 2. It just seems far easier to set up and string a load of songs together. It's simple to mute and adjust tracks you dont need.
Personally I don't use midi or kar files myself when playing but I do backing tracks for singers and groups using PC and Mac sequencing software then saving them out as MP3 files to a CD, mini disc or dat tape so I know where you are coming from and what sort of thing you are wanting for your band.
The G70 and Korg, I've no idea what their smf/gm/gs etc playback is like. Go for the cheapest The G70 and SD1 with having 76 notes rather than 61 may be more bulkier to carry about?