Diving into the world of tubes...help needed!

Wolf, I know you were thinking of purchasing the Pass XA25, as was I.  How do you like the Aegir and has it stopped you thinking about the Pass?

It's about time you decided to get into tubes, I bet you will be very glad.

Before tubes, speakers.

Speakers, properly matched in the listening space is by far the most important in any system. Speaker efficiency more important when using tube amplification (not a concern for tube pre-amp).

I understand liking/loving the Focal 906 for a bookshelf situation, like I love my B&W's in my office, but not for the primary music system. What is your listening environment? By the way, I added a powered sub to my B&W's in my office, add just a bit, only aware when you turn it off. Do you use a powered sub-woofer now? I'm not saying you have to have more bass, just want to know more about your goals.

Always consider speaker's efficiency, and speaker's impedance when selecting how much tube power you need.

Focal says efficiency 89db, that is my 'threshhold' for tube power.

This review measured 87db. (not a proven fact, just came up in a quick search, I don't know anything about your speakers or the reviewer), but, if true .........

" The Aria 906’s sensitivity measured 86.8dB/2.83V/m, which is typical for a speaker of this size and configuration. The impedance remains above 8 ohms from 700Hz to 20kHz, and dips to a low of 4 ohms at 200Hz, but never lower." Not a fact, just a quick 

It is said, +3db is needed to have a basic perceivable increase in volume. For any amp, double the power is needed for +3db sound level, so, -2db efficiency is more limiting than you might imagine.

To keep tube power requirements fairly low, i.e. 20-45 wpc  (whole lotta more choices, whole lotta money still in your pocket) I would want more efficient speakers, with more bass from them, or, a stereo pair of powered subwoofers, IF the space allows it. 

Ports: None, or front only like your Focals. Avoid side, rear, bottom ports, too much potential for difficult room interactions.

 

I have a Prima Luna and think its great.   It's a power amp so I can't comment on the pre amp part but you would do well with your own inexpensive pre and a power amp.  The power amps are inexpensive, depending on the model.  I bought a prologue 5 and it was cheap . 

Getting into tubes.

It is very important to define your system needs, think carefully about control options, both manual and remote. Inputs, future additions, ...

Bias Adjustment of Power Tubes: external, easy, safe, is a very desirable feature for tube amps, I wish I had it, I don't. 

I am just now learning about some modern control/input choices, I'm 71, tubes, LP, Reel to Reel, using old school McIntosh tube tuner/preamp mx110z into tube integrated amp, Cayin A88T. (I love the sound of the Cayin, but I may change for a few reasons).

Tone Controls/Balance. I agree with you, controls are important when needed, often just a bit improves a lot. Most important for me is balance, and much preferred is remote balance. I started a thread about remote balance

https://forum.audiogon.com/discussions/remote-balance-control-on-tube-integrated-amp

I don't use treble/bass much, but if I did as you describe, I would also prefer that remote controlled. Remote volume, and mute also.

One option, is to effectively have 2 systems, some equipment direct to tube amp, some equipment thru tone controls, then to tube amp. I use this Chase Remote Controller for a few components, it then goes to my tube integrated amp via it's AUX (any line level input).

https://www.ebay.com/itm/CHASE-TECNOLOGIES-RLC-1-REMOTE-LINE-CONTROLLER-Complete-In-Original-Box/123978156682?hash=item1cddac8a8a:g:0CsAAOSwUHld0Ht4 

It can also be used via a tape out/in loop

As it says, absolutely no noise, Cannot tell if it is in or not in the loop.

Some equipment has tone control bypass options, and some Integrated Amps have tone controls for a few inputs and also have 'preamp in' which skips the Integrated's tone controls.

Those features put you into a modern Integrated Amp. Some, like the Vincent you mentioned, are hybrids, only preamp is tubes, amp is Solid State. I would go tube power as well as tube preamp.

I highly recommend McIntosh Mode Control IF it fits in your setup

stereo/stereo reverse/mono/l to r/r to l/l+r to l/l+r to r. ...

I use this to get my speakers matched. They have presence and brilliance controls, and need to be carefully and properly adjusted. Cassandra Wilson; Richard Burton; No More Tears Duet with Barbra Streisand and Donna Summers help. I find test records are best for TT refinement of Anti-Skating l/r balance.

Above done, if the balance is off a speck, it's the source, and a small tweak can be a magic improvement, not just a 'fix'.

My Cayin A88T was designed in Germany, made in China, point to point wiring. Designed to sound like a McIntosh 275.

Used, off warranty. The reviews gave me confidence. It's price very compelling. No regrets, it sounds terrific.

I took the bottom off, it is incredibly impressive, exceptional build quality, and, the layout allows space for any technician to repair if needed.

Unfortunately, to get 16 ohm taps, I had to get the version with internal bias controls. OP's existing speakers use 8 ohm taps, so finding external bias control should be easy.