30 year old player, worth an upgrade?


Nothing wrong with my 30 year old Marantz CD40 player but is feeling an itch to upgrade.
My current amp is the Bada Purer 3.8Mk hybrid bought new 5 months ago.
Will any of these players provide a definite improvement in sound quality?
1) Nad C568
2) Bada HD23
3) Marantz CD6006 (used)
I do not have a chance to home audition any of these so would appreciate any inputs you may have.
The first two retails at about the same price while the third is about 40% lower.
Thanks!
ertorque
I don't know what your budget is, but I think that player has seen it's day as far as it's transport and the DAC. Remember, the chip is only part of what's important. The rest of the DAC and the way its implemented are just as important. I think that you would get a lot more satisfaction from a newer player with a better transport and a non-oversampling DAC. 
A used Audio Note would be great, or a reliable transport and an Audio Note Kits DAC. 
@ertorque:"

"The CD40 does not have digital outputs. It is the cheapest Marantz player that has the TDA1541A chip"

My bad-- I should've suspected that a CDP that old might not have digital outputs.

keep in mind, if you do go with separates, you'll have a lot more choices in terms of your preferred sound, due to the significant differences between DACs. 
A used Apollo-R, excellent sound on its own and can be used as a transport should you decide to move to an external DAC.
I added a $130 Topping E30 DAC to my 30 year old Denon CD player, and it made a notable improvement.