going to tubes, just one question..

I'm re thinking my entire roadmap for upgrading..I plan to leave my SS amp/pre amp behind for tubes. I've caught the vinyl bug and I think tubes will only enhance my experience.
I can't get my head around one thing. What rule of thumb should I be using when matching power/current to speaker loads, i.e. power hungry speakers driven by 8 watts...? Can someone tell how this is possible? My fear is shortchanging myself on power and current....
Budget for both amp and preamp, say 3k