Harm, if the speed -six is in .357 Mag and in good shape get it. They came in both .38 Spl and .357 Mag so make sure which it is. They were offered in blue and stainless w/ either the 2.75"bbl or 4" bbl. they are very stout, accurate guns. They also break down for cleaning much like an autoloader, without tools once the grips are taken off.
As the Norseman stated the little factory wood service grips are not very comfortable with Magnum loads, so at the very least get a Tyler T-grip, or Pachmyers, etc.
So $375, for a Speed Six in very good condition is a good solid price. At this time, the old classic revolvers from all the major mfgs( S&W, Colt, Ruger, Dan Wesson) are selling at ever increasing prices, there is a booming collector market for the 2"-4" service revolver niche, w/ most very good-excellent examples starting at $450 ( if your lucky) and up.