As far as I understand, the only difference is the size of the manifold. They have gotten a little smaller over the last year or two.
It's all good. I had googled the prices on the new units because I forgot what we had paid for ours. Based my asking price on what I had found in the first couple of results. Also poked around eBay to help. I don't mind beating those lower prices though. Just looking to clear out some unused equipment to make room for new stuff.