Should I be able to hear a 4Hz difference in my speakers?

Should also say, as some one who loves 2-way speakers, if you want to hear better bass, consider the room acoustics. They can make your speakers sound bigger and tighter. Talk to GIK Acoustics and in particular ask them about their soffit traps.

I most recently went from Vandersteen 2Ce Sig II (manufacturer spec -3 dB at 29 Hz) to Thiel CS2.4 (manufacturer spec -3 dB at 33 Hz). Using a tone glide in my system/room, I could hear some output from the Vandersteens down to the mid 20s. With the Thiels, I don’t hear much, if anything, below ~30 Hz.

But in terms of music, the only song in my collection where I could hear a difference in terms of bass *extension* was Tracy Chapman’s "3000 Miles". That song has an organ tone that had at least some weight via the Vandersteens but is barely audible via the Thiels. The Thiels can reproduce everything but the left most key on a piano, so they capture virtually all musical content. In regards to bass *quality*, the Thiels are tighter and better defined than the Vandersteens.

So, yeah, I think it’s possible to hear the difference in bass extension between those Totem models but only on a tiny subset of songs.

Should I be able to hear more bass with the Forests 

It depends how much louder the forests can do 28hz than the hawks. If its only 1db you wont hear it. If its 10db you obviously would. Find out how much of a difference there is. 

neither speaker is putting out 28 hz or 32 hz at full volume to the listening position, so many other factors at play...properly set up and with good room acoustics the Forest bass will sound better and deeper...

You must realize that the specification is measured for a specific response (power level).
At 28-32 Hz the amplitude will be at any where from -3 db to -16 db or more.
Only if the range (25-35 Hz) is audible.
And yes you should be able to discern this difference.