Choices for visually impaired users

I am visually impaired (macular degeneration). I moved to my imac five years ago because of the easy to use zoom facility. I am ready to upgrade and consider the following options:

1. A 27 inch imac. This is slightly better than my existing 24 inch but when I display music notation I need to zoom in so far that I only display three bars.
2. A mac mini coupled with a 40 inch TV. This screen size enables me to view a complete line of music but I'm slightly concerned with the lower resolution (1920 x 1080) especially when I zoom in to read text.
3. A mac mini coupled with two 27 inch high resolution monitors. I'm not sure if this is possible and if a single application such as sibelius can be displayed over two screens. In addition, would the zoom facility work as usual?

My processing requirement is not heavy so the basic configuations in both machines are more than adequate.

Any help, views or experiences will be much appreciated.