Which amp would you choose and why - Pass Labs XA-25 or First Watt F8?

I'm very interested in Nelson designs and hope to upgrade to his low watt offerings for a smaller room I have. Does anyone have experience with the Pass Labs XA-25 and First Watt F8 amps? Both are rated at 25W. What main differences do they have? Which one has better bass?

Preamp: Cary Audio SLP98
Speakers: Tannoy XT8F (91db efficient)