I've narrowed it down...

Buying an amp for your current speakers with plans to replace those speakers is not the best idea.

"speakers will have a greater effect on sound than amplifiers..." And not by small margin IMHO. OP, what is your budget for an amp and speaker transition? Even if done in stages?

2K for integrated amp.

No budget yet for speakers.

My current (HT) setup...
Reciever; Pioneer VSX-94txh
Front; B&W 602 S3
Rear; B&W 601 S3
Center; B&W LCR 600 S3
Sub; Outlaw LFM-1

The 602 S3's will act as the speakers for the time being until I make the dedicated 2ch speaker purchase...

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

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?

Unsound, you don't get it, or misread my post, where I basically agreed with your premise under ideal conditions. So, let me give you another example where it might not work out that way.

Let's say I'm a newby like we all were at one time. I put good money into a SS amp like Threshold, SS Pre, big name brand inefficient speakers and ancillaries. Then, over time after listening to many pals systems, going to some dealers in my area and the big Audiophile shows I realized I liked the sound of low-powered SET tubes best of all and wanted to make the transition from SS to tubes.

What to do? I have a bunch of funds tied up in my SS rig and modest funds available to me, yet since I've done some preliminary thinking, at least I know I want tubes, I'm going to liquidate my SS stuff on Audiogon and elsewhere. While I'm in the process of doing that selling, a friend offers me a really good name brand SET tube amp, that I have heard and really like with various speakers, the price is good and I can afford it. I take the plunge and purchase it. Now I have the amp and know I must find a synergistic speaker match for my listening room and my listening preferences. Of course I have a pretty good idea where to Start.

So, in short the chicken or egg can go in either direction. It might depend on your individual circumstances. So, what is the big deal about auditioning speakers with an amp I know I already like. Not any harder than buying the speaker first and finding an amplifier IMHO.

I don't think that 20 watts is adequate to drive the B+Ws, regardless of the amplifier's implementation. The ones that you mentioned in your original post put out around 70 to 90 watts, and that should be fine. I don't think that you'd shorten the life of a tube amp (or the tubes themselves) by using one with the B+Ws, that was not the experience that I had. It just didn't sound good; in my case, everything just sounded flat. You mentioned that you're moving, so maybe the thing to do is wait for a bit, get settled first, figure out your 2-ch listening space and then look into buying an amp and speakers at the same time.

-Mike