Pass INT-25 better than Wilsenton R8?

Both amps have different sonic profiles. I am not surprised enjoyed the tube presentation more than solid state even though it is a renowned brand. If the pass is not broken in then you may wish to reconsider.

Yes, make sure you have at least two or three hundred hours on it before deciding.

Also, yes, tube and solid state will have different character. Over the last 50 years I have slowly moved to all tube equipment. If you are not thrilled by the time your unit is broken in I would look at a Audion Research Vsi75. Spectacular sounding unit… detailed but beautiful midrange bloom and bass. 
 

I have owned high end Pass for nearly 40 years… including a preamp. while I love his excellent equipment I found the preamps a bit too sterile. 

As others suggested, give the amp minimum 300+ hours before you decide. I'm saying this from direct experience with the INT-25 which I still own and I think this is the best amp money can buy under 10k. I was also "meh" at the beginning and was not sure if I did make side or forward move (previously have owned Pathos Classic MK3). But after approx. month and a half the amp opened up like crazy. The transparency, instrument separation, soundstage all of this improved. You have a great amp in your hands, don't loose it :) 

Not directly related to OPs question, but does anyone definitively know if the amp section of the INT-25 is identical to the amp within the XA25?

I have a Willsenton R8 in my second system right now, and it's terrific. It's not better than the Atma-Sphere gear in my main rig, but it's perfect for the living room.

Everyone is correct that you need to give the Pass some break-in before you can make a rational judgment. I'm not familiar with the INT-25 but I've owned a couple of Pass clone amps and it should sound great. That doesn't mean you'll necessarily like it better than the R8, regardless of the price difference.

After a reasonable break-in period for the Pass, trust your ears.