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

The XA25 is the much "safer" choice in that it has much more power and is stable down to 1/2 ohm.  From everything I've read (and I had the XA30.8 paired with similarly spec'd D7's), the XA25 will have better bass and silkier mids.  The F8 may sound a bit more agile but possibly lean in comparison. Your Tannoy's can go as low as 20hz and the impedance dips all the way down to 2.9ohms at 100hz.  I really think you will need the XA25 to drive those Tannoy's properly.  What amp are you using now?

@ghdprentice +1

Completely agree and I have had several examples just in my own house. My Leben 15w CS-300xs sounds substantially better than a Cary SLI-80HS (80 watts ultralinear) with my Forte III’s. The Leben also far outperforms my 30w Sudgen A21SE with the same Forte III’s. My Pass XA30.8 (30w) paired significantly better than another Cary 120w amp with my Spendor D7’s. Circuit topology, transformers, impedance matches, etc all matter when it comes to amp/speaker synergy. It really is not as linear as just saying "get all the power you can" to ensure a good sound. That works sometimes, but not in every situation.

I own both. The XA-25 will play a bit louder and more dynamic than the F-8. I listen to the F-8 religiously acct. it sounds more musical, sweeter & more accurate than the XA-25. Plus it is a more intimate sound. All my listening is thru LS 3/5A speakers. I own many low watt tube amps and I still listen to the F-8 above all of the these.

@powder99

Problem is the OP has Tannoy speakers that dip down to 2 ohms. Your LS3/5A’s are 15 ohm speakers. This is a huge difference. I’m sure I’d prefer the sound of the F8 into your speakers over either amp into the Tannoys.