I've narrowed it down...

I think that a tube upgrade would certainly increase the quality of the sound I currently have, the question now is would my existing speakers cause damage to an integrated tube amp? When you say hard on a tube amp what does that mean? Will i need to replace 5000 hour tubes in 20 hours or after 4500 hours?

Once I have the integrated I want/can afford, I will consider speaker replacement provided I wont do damage to the integrated tube amp driving my existing speakers.

Phase angles? Dips? Capacitive angles? What is this you speak of?

and... what is a reasonable amount of power to consider? is 20w/ch enough are tube w/ch different than ss w/ch?

Botit,

I think a tube amp will sound fine but it will not be especially robust because the impedance of the B&W is too low which robs some of the power of the amp, also it may exhibit some of the traditional 'tube' amp characteristics which is big bass and/or rolled off high end.

I do not know the electrical end of it so others might help here.

Botit,
Phase angle? Well, a resistor is sort of a pure load. Any energy stored is generally as heat. Voltage and current rise and fall together.

With capacitive or inductive loads, voltage and current do NOT rise and fall together. Tubes typically do not like driving a load which looks too much like a capacitor. Both inductance and capacitance are 'stored' energy = reactance.

There is some math involved, but basically, the angle between voltage and current determines how much power is actually available from the amp TO the load to do actual work. At 90degrees, NO power is available. So, in a high reactivity load you may not get 'advertised' power.
B&W is demanding of an amp because it is reactive at some frequencies.

Look up Power Factor. The Wiki article is simple and has illustrations.

As for impedance, lower also makes more demands on an amp. Speakers are rated at a 'nominal' value, but can vary a LOT from that value. At the more power demanding end of the spectrum, say below 300hz, a large dip in impedance at the same place as a large phase angle will result in large demands on an amp.

Here is link to the power cube way of measuring amplifier performance. Note how some 'poor' amps fall down when asked to drive hi phase angle at low impedance. Even some good amps don't necessarily shine in this test.

http://www.audiograph.se/Downloads/PowerCube_12p_brochure_complete.pdf

Make it Cayin, great sound, great value.