Ray, if it's 180fps without the foam/carbon and 184 with it, that's an increase of speed by 2.2% (gots to move the decimal when using % bro).
To put that into perspective, it's often said that 1" of draw = 4-5 fps depending on the bow and 1# of draw weight is often equated to 1fps. So 4fps would be going up 1" in draw length or 4# of draw weight.
If you're into kenetic energy, 640gr@180fps=46 ft/lbs. The same 640gr@184fps= 48 ft/lbs, that's a 4.3% increase in Ek (dat's kenetic energy in physics speak).
If you're into momentum, 640gr@180fps=.511. The same 640gr@184fps= .523, that's a 2.4% increase in P (dat's momentum).
(Dang, I knew I'd use that Georgia Tech larnin one day)
If you're into quiet and perceived smoother draw...well, I have no calculation for quantitative analysis but my cranial computer says the carbon/foam longbow limbs are superior to other models.
I think every feller should shoot what he wants, whateve his justification, and I know my brother Ray feels that same way too.
I know my justification is partially made considering "efficiency" more than it's by-product "speed". While it is "down the list" in my criteria for a bow...it's still on my list!