I talked to HB Friday morning. There are no needed transducer upgrades allowing for better imaging. My understanding is the gen3 units have more voltage allowing greater side imaging range. The 2D imaging has more resolution. Otherwise the gen 2 and 3 are basically the same unit.
They have discontinued the gen2 and they are $999. The Gen 3'-s are $1500.

I have a new helix9 si gen2 sitting beside me on the couch. Thanks again guys.