I currently have basses here with bodies made of Swamp Ash, Poplar and Basswood...and then one that could be made of Maple or Alder or "the Finest Select Hardwoods" but I don't know which.
I think the sound characteristics of most of them are more defined by the pickups and neck materials than the wood the bodies are made of.
The Peavey Super Ferrite pickups in the Foundation have a unique enough sound that it is pretty hard for me to compare to anything else, so what body wood was used seems secondary.
My Peavey G Bass had the highest MSRP when new. Peavey says it has a "solid basswood body" (that many people equate with budget basses)...attached to a 35" scale carbon/graphite composite neck!
It has one internally active Peavey made pickup and a Peavey made 3 band active boost/cut tone circuit.
Between the graphite neck and the active tone circuit, I am not sure that the body wood is a real important factor, also there is nothing out there to compare it to, so I don't know how the body wood plays into the sound.
My Warwick Rockbass $$ has Ash body wood, but the two MM style humbuckers placement and the series/parallel tone option probably characterize it's sound more than the body wood....I would guess.
To the best of my knowledge, most US Peaveys were Poplar, a few of the higher end models Ash, and some of the neck thrus more exotic woods.
I think you are right, most of the Peavey basses I've looked up are poplar, but I was surprised by how many different body woods got used over the years with the Foundation basses.
Did you sell your Forum P-J and remaining Foundations?