that I would be, if not blown away by, at least much happier with a set of 2 Infinity 150s and a C25 up front in my home theatre in place of my current 3 bose model 100 speakers?

Would these Bose model 100s be OK for my rear surrounds? Currently I am using some very small Sony home theatre in a box surround speakers in the rear.
I would consider some 140s for the rear but they must be turned sideways do to space constraints.

In most cases, it is NOT safe to assume. You remember what Felix Unger said, don't you?

In this case, though, your assumption is correct.