i have a 1984 pair of kg 4's - unlike others i have heard about the back panel says 'nominal impedence 4 ohms' - did they make two versions of this speaker? - and while my fisher 500c will work in 16,8 or 4ohms would the amp perform best in it's 8ohm position as the recent stereophile review of this receiver says it does - would the 8ohm tap damage the speakers performance in any way? - thanks,