Where do I start-amp or speakers ?

This reminds of what came first, the chicken or the egg or in this case the amp or speakers. Do your research on speakers as to which will offer the best sound for your dollar, also keep in mind that the more sensitive they are, the less money you will have to invest in amplification. I'm not talking less sound quality but less power.

Sometimes the speakers that require less Watts, seem to want more expensive Watts.

You can't buy speakers without considering what amp you will be buying. They work together or not. You have to hear them in combination or there's a chance you'll be disappointed.

Ya, amp- speaker pairings are the most difficult pairings IMO,
and I know others agree.
. You have a huge room with those tall ceilings, more room for reverberations, but also more space to fill in with sound. I have learned to start with speakers that aren’t too extravagant so they can be matched with a good variety of amps at reasonable cost.
I have the Spatial M3 Triode Masters, price= $4000.

Now before anyone writes off these “Triode” Masters, these speakers don’t require vacuum tubes, and they don’t sound like tubes. They will fill the room with sound, they have two 12” cones with a voice coil on the upper cone. Very broad soundstage, SQ is equal to about an $8000 speaker, and that’s not hyperbole, b/c Spatial sells direct to the customer, so huge savings. Also, a 20 year warranty. Who does that these days? (Made in America too). Ok, I sound like an ad, I’m done.

Spatials are linear, and beautiful but punchy sound,and technically 16 ohm, but does require alot of power to drive them, more than just a small tube amp. One guy posted that he ran the Spatial M3 Triodes with the Schiit Freya and Schiit Vidar SS monos to great success. Vidar are like $7-800 each.
And if you already have the Freya, you’d be guaranteed great synergy using the Schiit products together!

Ive also ran the Spatials (and Dynaudio Contours, & Dali Helicon 400s) with the Primaluna Dialogue HP Integrated amp.
$4300.
Can run Triode or Ultralinear via remote. Can runs any tubes from EL34 to KT88 to KT150 for power section. 70 lbs. 3 huge transformers will give you the bandwidth you probably want coming from using the  Krell/Thiell combo.  This amp has twice as much power as needed for the Spatials, so you could also try the little brother, the Primaluna Dialogue Integrated, $3300

. I don’t know if you are open to tubes, but the Primaluna is another exceptional value, is not “tubey” sounding, is not soft, and is not slow.
This amp manhandles the Spatials, and can drive other speakers down to 2 ohms! 
So down the road, you could also try electrostats or other notoriously “hard-to-drive” speakers.

Amplifier speaker integration is only hard if your speakers have a hard to drive impedance curve, and if your amplifier has a high output impedance. Avoid those two problems and there is no real issue unless you are a hypochondriac.
If the budget is indeed 8K for a medium sized room, I would allocate most to the speakers: Harbeth SHL5+ are perfect for such a room, and they are easy to drive. Harbeth make some of the cleanest, musical and non fatiguing speakers on the market. They like a bit of power, so why not go for an affordable solid state pro audio amplifier like the 2x350 watt Yamaha P3500s? See here for a test that proves that it is perfectly suitable for domestic use: http://www.homecinema-fr.com/forum/amplificateurs-de-puissance-haute-fidelite/mesures-ampli-yamaha-p...
I recently bought the slightly weaker 2x250 watt P2500s for my son, and the sound quality is just perfect. The variable speed fan never comes on in domestic use. And as a pro audio unit it has balanced inputs for lower noise. Built like a tank.