AR CD3, CD5, or CD7?

I've been getting back into 2-channel after some time away. I recently purchased an AR 300.2 amp, AR LS17 pre, and Magnepan 3.6 speakers. I have an older cd player (Rotel 971) that I would like to replace. I would also like to keep to the AR product line. Any thoughts of whether I should go with the CD3, 5, or 7? The 8 is a bit out of my price range. I know auditioning is the best way to go, but the only player dealers have in my area is the CD7.
I have been using the CD3 MKII in an all ARC system for several years and am quite well satisfied. While my listening comparisons to the upper level ARC players reveals they have improved, nothing has yet convinced me to spend the extra $.

The CD3 MKII is very detailed and quite accurate across the board and is intimately listenable for hours on end. I play it and my TT about equally, and find some material better on one and other material better on the other. It is best to listen if possible to both in your system, however, we all know that is sometimes difficult or impossible.
I can't comment about the choice of ARC CD Models, but I can say that staying with ARC componets throughout the system will likely insure that the nasty hums and buzzes that plague many system will be minimized. I also feel that leading edge companies like ARC design their gear with certain sonic attributes in mind which may never be realized with a 'hodge-podge' of different componets.
As Eee3 stated, it all depends on your budget. I now use the CD7 and previously owned the CD3mkII. To me, and speaking only for its use in my system, there is a noticeable improvement across the board. Better tonality, clarity, rhythm, pace, dynamics, micro-detail, noise floor, etc. How much better, and how much that difference is worth, only you can decide. The CD3mkII is a great player, and for the money, is very tough to beat. With your system, I believe either player would provide great synergy.

By the way, your LS17 preamp is a real sleeper--definitely underrated and a great piece of gear. Happy listening.
If you can afford the CD-7, that's the way I suggest you go. I have one in my system and like it very much.