Multiple DVD Players

Is there a way to hook up multiple DVD players to a TV or preamp? Like half a dozen?

My Samsung TV has only two video inputs. My Harman Kardon Citation 25 preamp has two "VCR" inputs and two "A/V" inputs. This should give me the ability to hook up 4 DVD players but what if I want more? Or am I wrong?

Maybe this is simply answered but I want to make sure I don't misunderstand something or goof it up. Besides, it very well could help others who are new at this stuff.

Why 6 DVD players? Well, this is for retirement. I'm planning ahead.

I want to load up 6 vintage TV shows on DVD's and change them out once a week or so, not every time I want to watch something different.

Thanks.