Power output of tube amps compared to solid states


I'm having a hard time trying to figure out how tube amp power output relates to solid state power output. I've been looking at the classifieds for tube amps and I see lots of tube amps with 50w or 60w output, but nothing close to the 250w output typical of solid state amps.

So I have no idea what type of tube amp is required for my set up, right now I'm using totem forests with a required power rating of 150w-200w at 8ohms. The bass is so powerful on these that I have the sub crossover set to 40hz.

My question is, are tube amps so efficient that 50w from a tube sounds like 150w from a solid state? Or will 50w output from a tube severely limit how loud I can play my speakers? If so, are tubes usually meant to be driving super-high efficiency speakers?

I had previously tried a tube pre-amp with a solid state power amp (both musical fidelity) and didn't like the results because the imaging suffered greatly, even though the music sounded nicer from a distance. Now I want to try a solid state pre-amp (bryston) with a tube power amp (no idea which brand to look at), but I don't know how much power output I need or if it will even be possible with my speakers. Does anyone know what I would require?
acrossley
Kirkus, Shadorne, and Unsound, I really appreciate your input over the years. Inside of what I call the Voltage Paradigm, yours can usually be counted on to be accurate comments, and always done with decorum :)

I want to point you to Duke's comment about the port tuning dated 04/12. Here Duke is pointing out how the port is set up differently depending on whether you are using Voltage rules or Power rules. Its not the only thing I have seen in speaker designs, as in crossovers I have seen capacitive or inductive shunts used to get the right power response out of the amp so that the driver will roll off at the right frequency.

I guess what I am getting at here is that the Voltage rules are not the only game in town, and this has always been the case. However I find that if I am dealing with an individual who is educated with Voltage rules, that they will generally assume that there are no **other** rules. So I am interested in you thoughts regarding Duke's post.
Atmasphere and Duke too, I think it's us (well at least I can speak for myself) that should be thanking you. Not many other manufacturers have been nearly as generous with their knowledge and expertise. It's encouraging to see such apparent enthusiasm even though you must be up to your eyeballs in this stuff each and everyday. I especially appreciate how difficult it must be to be financially vested, yet enthusiastic, while maintaining the level of decorum that you consistently do.
However I find that if I am dealing with an individual who is educated with Voltage rules, that they will generally assume that there are no **other** rules. So I am interested in you thoughts regarding Duke's post.

On the power rules front I think that provided a speaker is well designed smooth load with no large impedance swings and no low impedance dips (i.e. a decent speaker design) and provided it is well damped at resonance (again good practice - although not always followed - even by revered manufacturers such as Wilson)....then the speaker should sound great with a higher impedance amp (i.e. no need for a ridiculous high damping factor if the speaker is well designed). A damping factor of 10 is generally much more than enough and may be far preferable to an amp design with oodles of feedback, a damping factor of 500 and stability problems that result in high amounts of transient or IMD distortion (everyone knows that overly high gain and overly high feedback can bite you when playing real world music to a complex load - no matter what a speck sheet sheet implies).
A bit off topic here, but, if a speaker manufacturer needs to veer from the criterion you use to describe a "decent speaker design" and needs use something other than a higher impedance amp to achieve better results, what's the harm?