The Marantz 63SE or 63Ki. Definitely. Very hard (and usually very expensive) to improve on.
Though by now, they're prone to have transport problems, like skipping tracks. There are two guide rods which I think were supposed to be self-lubricating, but a very sparse application of lithium-based grease usually fixes that problem. (I did that for a friend and his is still working perfectly five years on.) Alternatively, a replacement complete mechanism (original, CDM 12.1, now hard to find unused; the alternative new is a VAM 1202) is not very expensive and not too difficult to install. There's an illustrated 'how to' at hifigear.co.uk somewhere; search for 'Marantz CD63SE'.
But: a word for the original (top loading with puck) Marantz CD-63. They were built to survive doomsday. (I always assumed that that early, Philips and Marantz were absolutely determined that their CD players were
not, never, ever going to die on anyone, because that would have doomed CD for eternity.) Mine is still going and was actually used for several months while we worked out what had gone wrong with a friend's Studer and sourced the spare. It's heavy and 16-bit; the programming is extremely basic and very slow—it's best just to press 'Play' and let it get on with it—the track readout is just a line of LED's and can't go beyond a dozen tracks or so, though of course it will play as many as there are on the CD, and there's no remote.
But it really does sound superb still. And after almost 30 years mine is (touch wood) showing no sign of giving up. (I've gone through four or five CD players since I got that about a couple of years after it was made, and replaced the cog wheel and drive belt on a couple of CDM-9 mechanisms three times . . ) There's a Philips that looks the same (but I think only came in silver: the Marantz came in silver or black) but the black Marantz sounds better than both. I hadn't listened to it for years, and I was very surprised. Someone (can't remember who) used one at an HFN Show around the late 90's with an external power supply as big as the player and it shocked everyone. I've wished ever since I'd got hold of the design or asked for one.
There have been a couple on
eBay recently. . .but for £500-£600, which I think could be a wee bit over the top . . .They haven't sold yet, or I'd be putting mine up for sale!