This is for Georgehifi especially but others can chime in.

Can we clear something up? All passives basically suck. It's unavoidable. Let's not confuse passives with buffers just because the stage isn't making gain. If it's got active devices, it's an active pre-amp. 

All passives basically suck.

Your First Watt amps have very little or no gain, I can see this maybe your reason behind this statement.
But that’s your opinion, and you are entitled to it.
It is a totally incorrect statement if there is no impedance mismatch or gain problems as First Watt amps will have, there is only transparency, dynamics, and distortion advantages over any active/buffered preamp with or without gain.

As quoted by Nelson Pass:
" What could be better? Hardly any noise or distortion added by these simple passive parts. No feedback, no worrying about what type of capacitors – just musical perfection."

Cheers George

@dsremer  I will be getting 260.8 monos from Pass Labs or 60.8. The XA 25 is not enough juice. I agree. I will have plebty with monos. I am going to stick with the XP 12 preamp. I’m enjoying all the suggestions and interesting asides on this thread.Thankyou everybody.

@georgehifi 

Say WHAT!?!?  Where did you get the idea FW amps have no gain? My F5 has about 15.5dB of gain. All but one, the impedance converting F4, have voltage gain. 

Real passives expose the source and the amp input stage to the varying impedance of the volume control. You can try to passively remedy that, but the source and amp are always going to see some wandering load or source. Buffering the volume pot or resistor ladder or whatever you like with something like JFETs provides a very high impedance to the pot and a very low impedance to the amp. And there's no reason you can't buffer both sides of the pot. You'll end up with vastly superior performance across the volume range. 

My F5 has about 15.5dB of gain.

Say yes!!! about half normal power amps.
Which is very low for a poweramp, and why your experience with passives is understandable, and why you need the gain of an active pre.
 
As Nelson said: " "We’ve got lots of gain in our electronics. More gain than some of us need or want. At least 10 db more."  

And there’s no need for active buffers, on passives if there’s no impedance mismatch.

Cheers George