Future: Downloading brochures will give you a good start. Grady walk-arounds have similar lines, and, from a distance, or in a picture, can look similar.
But if you can get to a dealer or a boat show, (or look at the prices) you'll see a world of difference between the Voyager and the Marlin. The others fit in the gaps, incrementally.
Also, three of the boats you mention are no longer made, at least not under those names. The Voyager became the Journey with an extension of the running bottom and not much else changed. The Islander left with no obvious replacement. The Sailfish grew a bit and became the Chesapeake (sp?) 290.
Good luck in your search.
Rob