Amp first approach to building a system, anyone ?

Big VAC tube amps are absolutely worthy of an "amp first" philosophy. Almost all my favorite/best listening experiences were heard with a VAC behind them. For me, a great amp is the most important component after speaker selection. And indeed, the biggest system investment is into my VAC amps. I like to listen loud and prefer the sound of tubes, so that makes it much harder and more expensive to satisfy on the amp front.

Selecting amp before speakers is a bit of putting the cart before the horse, but I can still almost see that, given a good enough amp. 

I'm pretty much amp first on the headphones front (electrostatics) too. 

mulveling, the amp is before the speakers !

In the perfect world I am a source first - best Studer you can find, then move from there, very simple. Table set ups are complicated.

Room treatment would come first for me.... If the room has sound bouncing all over the place off of flat reflective surfaces, for example, you can spend all you want on gear and nothing is going to sound very good. Of course, this is not an issue with a headphone system. 

Never ever ever has a Room undergone room treatment as the first approach to creating a Audio System.

Over in the UK VAC Amp's do not appear too often, but unusual as it is, there are Two different VAC Models used by Members of my local HiFi Group.

One, which is a older released model I have been demo'd on a few occasions and the other I have not heard in .

The one I am familiar with is superseded by a 300B Low Watt Power Amp'.

Personal Preference for an End Sound is exponentially varied across individuals who enjoy purposely creating a system to experience recorded music.

One persons maxed out in Transparency, " That's all I can take" is to another, a noticeably Rich Tone of produced sounds. I witness this regularly when at demo's with a large Group, the assessments voiced are sometimes total opposites in the description.

Individuals are with differing levels of sensitivity / tolerance to certain presentations of sound within a small space. In a Large Spacious listening environment, there is much much less, if any difficulties with tolerating the sound produced.   

Personal preferences definitely vary wildly, and I mean among people with good hearing, but when the sound is excellent everyone will agree with that regardless of the preferences.

Yeah, room tuning comes much later, not at all in the beginning.