I just wanted to update this thread in case someone is looking for a reader with the same constraints I listed in the original post.
I now have the PB360, it arrived yesterday, but my computer won't recognise it and now found a thread on here saying it might be my OS which is the problem. That was one of the major factors in buying the PB360 - I'd been told it would work.
I am trying to solve the problem with help in this thread here:
https://www.mobileread.com/forums/showthread.php?t=65136
just in case anyone is having the same problems with tiger. Not a happy reader right now!!