I have had the CD6000 OSE KI and in my view, it is better than the CD6002 but not so with the CD7001 KI. Also, I found that the quality of the sound improved tremendously when I switched the amp from a PM6010 OSE KI to a Rotel RA-04.
I was thinking the same a while back, but mainly because the transport of the CD6000KI sucks, sometimes perfectly clean and new CD's get a "DISC ERROR", but being persistent helps, after a few tries the picky CD6000Ki plays the discs.
I listened to both the CD6002 and the CD7001.
The CD6002 is lively, dynamic and at times over-enthusiastic in the high frequencys whereas the CD7001 is understated, gentle and observant.
I think the sound characteristic of the CD6000KI hold the middle between the two newer players, which decided me to keep the CD6000KI.
Having said this I am somewhat worried about Marantz's sound filosophy, there doesn't seem to be a solid consistency, the so-called 'house sound' doesn't seem to apply to Marantz.