Polk LSI speakers are good value for the money. I used to own a pair of LSI 15's, and they were a good match with tube amps. The ring radiator tweeter is a real treat.
I sold them recently, and replaced them with a pair of Source Technologies 277SE. Although the 277's are a bit smoother overall, the Polk speakers are very competitive. A buddy of mine has a pair of LSI 25's with a restored Fisher KX-200, and he loves the sound.