Need some Tube and Class A SS Suggestions

How many hours are on your D7's? I have a pair and they take quite a while to run in.  At 150 hrs you will notice the tweeter more relaxed and they keep improving so up to 500 hrs.  Well worth giving them time and the music sounds great along the way.  

I took a similar approach as you with my D7's as they are the most "hifi" sounding component in my system. Class A solid state amp coupled with tube linestage and tube phono stage.  The Pass XA25 will be a great match especially if you pair it with a tube linestage.  I use a XA30.8.  You will get the sweetness and open presentation of the tubes but with some bottom end grip that SS provides. I pair the XA30.8 with a VAC Ren MKV with NOS Mullard 6922's and I get everything that I need in terms detail, tube goodness, grip, texture, natural presentation, and balance evenly across the sonic spectrum.  With the amazing imaging, ability to convey tactile elements of music (they are really fast), and amazing bass down to 29hz, the D7's deliver a lot of value for the money in a fairly small package. I don't have experience with the preamps you're considering but I think you're on the right track assuming your musical priorities are similar to mine.

Enjoy!

@millercarbon is correct here.  The D7's aren't too revealing and that's a fairly nonsensical term I agree since it is an attribute we desire.  In my experience over the past 2 years with these speakers is that the tweeters need some run in to shed some initial grain and edge.  I first heard the D7's at a show and was hugely impressed.  I knew that Spendor didn't bring any D7's to shows with less than 500 hrs on them so I wasn't alarmed by the run in period needed.  They really have one of the most amazing tweeters I've heard...which I'm sure led Stereophile to write this  in its review: 

I noticed especially fine treble dispersion and extension, as well as freedom from any harshness. The treble had a crystalline clarity that put the Spendor D7 among the finest speakers I have heard at any price.

The tweeter clarity is at a level that most speakers don't possess.  They also have a fabulous midrange and bass extension while imaging at a level that I normally associate with nice stand-mounted monitors. In my system I truly enjoy the music that is conveyed through pairing the speakers with Class A SS amplification and a tubed pre that can operate in a fully balanced circuit from input to output. 

The only time I get infrequent high frequency distortion/edge/glare revealed by my D7's is with a digital stream in my system.  It never appears with vinyl. I use an Auralic Vega G1 and I suspect I'd need to move higher up in the market to get something digitally with a more organic presentation.  The thing is that I have zero interest in putting money into a digital front end.  Sure, it sounds pretty dang good but I use it mainly to explore new music and find new ideas for purchase on vinyl...or as background music while I'm working around the house.

I would be curious among this group whether they notice the strident tone only with digital as well.     

@shahram   

Balanced outputs are not a major consideration. More of a nice to have.

When considering a new component, it's nice when the design elements help give you the most flexibility in the future and get the most from your other existing gear - it just reduces the risk of wishing you had considered your criteria more thoroughly before buying.

For instance when I bought my Pass XA30.8 (fully balanced circuit) I did so with full consideration that my existing preamp used a transformer- coupled Class A1 balanced triode design.  It's just one of those things where if the price isn't any higher and you like the sound at least as much as your other choices it help cinch the deal because you're getting more design synergy for your buck.  At least that's the way I look at it.

@shahram   

But part of me really wants to hear what this speaker can do with a Tube power amp...the dilemma continues!

You likely won't come close to getting the low-end grip (both weight and speed) of SS with a tube amp and you will almost definitely get more noise.  I moved from a tube amp to SS with my D7's and knew the second I turned on my Pass XA30.8 that I had made a transformational improvement even moving to amp with half the watts as my prior tube amp. 

@shahram

What tube amp did you use previously?

I had a Cary CAD120S MKii, rated 60w in triode and 120w in ultralinear. Even in UL mode it didn’t come close to driving the D7’s like the XA30.8 can.

When you are listening at what you consider a loud volume, how far do you push the volume knob? Or where do you never go past on the dial?

When listening to a digital source (streaming in my case) I never turn it up past 10-11 oclock on the dial. That pushes the level up to 95dB or so listening 9 feet away. And the preamp I’m using only provides 10dB of gain. When listening to vinyl I rarely go above 12 oclock.

I’d say most of my listening is around 80-85dB and I’m somewhere between 9-11 oclock usually depending on source.

@shahram   The Pass is better from top to bottom compared to the Cary.  There is simply more weight, texture, and saturation across the entire frequency range.  There's a blacker background and hence more dynamic range.  Plus the soundstage is much bigger and the imaging is better defined.