Kevin,
My understanding is that the Model One is essentially a 6 ohm load. Am I misinformed? Be that as it may, I have absolutely no issues with the bass on my amp with its 8 ohm output, down to the limits of the speakers. The subs make up for the speakers' shortcomings, not the amp's. I hear no difference in bass extension between my PX25 and my Triton 300B amps, though the bass resolution is better with the PX25.
On the question of tubes, I just dont like the TJ PX25 that Gordon swears by. I find it overly warm, too bloomy and rolled off. I think the KR tube is far more neutral, transparent and extended - at least in my amp. Maybe that means I don't like "real" PX25's? So be it. The KR tube in my amp is a stone killer. Get Joe Fratus' opinion as well of the two brands before you make up your mind.