I totally disagree with some of the posters above about electric guitars and tube amps. The tonal density of electric guitars is represented MUCH better on my current tube setup than any of my previous ss setups. Tubes are not necessarily about "warmth" as much as density of tone. Now, granted my amps are way outside of your suggested price range.
You didn't mention if your budget was for just amps or amps and a pre. If you are looking at that price range for an integrated, I suggest you look at a used Manley Stingray. I doubt you will be disappointed, and it will drive moderately efficient speakers.
As for driving B&W speakers, I would tend to agree with others that tubes in your price range might not be a good match.
PMB
You didn't mention if your budget was for just amps or amps and a pre. If you are looking at that price range for an integrated, I suggest you look at a used Manley Stingray. I doubt you will be disappointed, and it will drive moderately efficient speakers.
As for driving B&W speakers, I would tend to agree with others that tubes in your price range might not be a good match.
PMB