I was using an HPA 2 with my Prodigies and the combo sounded pretty good. The bass wasn't as good as I thought it could be, and thought it was a limitation of the speakers. Well, I sold the HPA 2 and bought a Pass Labs X350 and the order of magnitude of changes were incredible. The bass significantly improved (tighter, lower, more definition) and everything else improved as well. Vocals are unbelievable with this combo. The Prodogies require a significant break-in, so give them time before determining an amp/preamp. The Pass X350 has been outstanding in every way and consider it a significant upgrade from the HPA 2, and the increased cost more than justified. There have been some pretty good posts on used and demo X350's. Give me an e-mail if you want to discuss anything further.
Frank
Frank