ADS 710 speakers /Sound quality and specs?

spec's can be found here.

http://sportsbil.com/ads/

Having owned/still own many ADS speakers, including the L710, you can do much better than the 710, even in the ADS line. Look for something more current, like the L780, or L880. Really nice are the L1290/2 and 1590/2. But the 710's are too dated, and sound like it. I purcheased a pair of the 1290's here on the 'Gon last summer for $325 plus shipping, and they were in excellent condition. Good luck.

I have a pair of 710's. I would characterize them as not as resolving and detailed as modern speakers (I also have ProAc D-15's)of similar quality, but they do have that musicality that makes them very listenable. They are 4 ohm, so they need a powerful amp. Bass is fine if raised up on the stands (which are worth something if original). $250 would be fine if in 8 condition, but watch out for rotting surrounds and grilles that are frayed or torn. I am not familiar with the Polks you mention. If they have regular binding posts and a fuse they are likely a "newer" version - I have the old spring loaded type which I know are not ideal. I believe they will hold their value if you keep them in good condition.