Opinions on Pioneer CS series speakers

the cs88a have their afficionados, though $500 seems high--they seem to sell pretty reliably for $250-350 on ebay. they're very early 70s, so you're gonna have to refoam + the tweeters and supertweeters tend to fry on these (though it seems pretty easy to get replacement parts). the cs77, which i haven't heard, seem to go for $100 or so. personally, i'd opt for something like klipsch (quartet, kg, klf), which are more modern sounding and very efficient, or for a current design like tekton or zu

Hi Saki70,
I have to agree with Loomis... I do see these go from $100 to $400 on occasion. They can be a bit tubby in the mid bass, but in the right room bass can be surprisingly good. The top mid range and top end are not world class by any means, but are respectable. If you buy them right and plan on keeping them, these speakers respond to modifications quite well.... i.e. cap replacements, and a little cone damping go quite far...
I would also recommend in a semi vintage speaker a JBL L100T or maybe one of the ESS models. In all the above be aware of rotting surrounds that you may need to deal with.
As far as SET Friendly. I have never seen true impedance or phase angle curves on any of these speakers, You will need to find someone with direct experience. I hope this helps, Tim

+1 on Loomis especially the Tekton/Zu recommendation. A used one would be a better sounding option and within your budget.