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)
128x128galacticmayan
Both are rated 25W into 8 ohms, but the XA25 is 50W into 4 Ohms and the F8 is 15W into 4 ohms...and many 8 ohm speakers still dip at times to 4 ohms or less...I think overall the XA25 is more powerful...many of the reviews of the F8 seem to include a comparison with the XA25...I loved the F7 with my Avalon Ascendant II speakers in a small room...
I havent listened to the F7, but have the XA-25 paired with a Cary preamps (SLP 98 and SLP 05) driving Spendor D9s (90db, 8 Ohm) and Chapman T7 (89db, 4 Ohm).

The Cary preamps and XA25 have amazing synergy in my system. The XA25 may only be spec'd as 25W but it sounds more in command of my speakers than the Rogue ST100 that I owned.
 I considered both these amps and even asked Reno Audio for a F8.  He told me to get a XA-25.  Said it was a better amp all around.  Took his advice and love it.  I have paired with an XP-10 pre and Salk Exotica monitors.  Wonderful, I have no desire to change it.