What's a good upgrade from a Krell 300cd cd player

The folks at Krell have heard and measured the differences.
The Dacs are different. Jitter reduction is WAY different. The 505 has TWO power supplies. The list goes on... Once again, the 505 is a huge upgrade from the MK III.

Zieman: The DACs are exactly the same> Three Burr-Brown PCM1738 DACs / The Transports are exactly the same / The 6 reconstruction Filters (4 for SACD & 2 for CD) are the same (though numbered differently) / Both use 2 Power Supplies> a switch mode supply to drive the transport mechanism and a toroidal transformer for the analog stages, with multiple stages of regulation / Both utilize a double box arrangement, and I believe that both use the same microprocessor. The measured specs are nearly identical, as per Stereophile Magazines's Dec. 2003 Review of the SACD Standard MKI and their Sept. 2008 review of the Evolution 505. I figured that the SACD Standard MKIII would compare closer still to the Evo. 505, since it was developed after the Evolution Player.

I would recommend that you spend more time on "the phone with the wonderful folks at Krell", before your next post regarding their products...

I agree with Elite, except that the 505 does use a new anti-jitter circuit and it may have made it into the newer SACD Standard III. They are pretty much the same.

I have also heard (from dealers and owners) that when used in “balanced mode” the Evolution 505 and Standard MK3 sound awfully similar, and that unless you own a full CAST system the E 505 is simply not worth the additional $4K (based on sonics alone – the E 505 is a much nicer looking and better built Machine). Outside of the “new anti-jitter circuit” as Joeyboynj had mentioned, these 2 machines share many of the same components. The E 505 was built-up from the Standard, and is not a new ground-up design, but is rather a "tuned-up" CAST version of the Standard – which as is reflected in Stereophile’s recent review of the E 505, turns out to be a very good thing indeed, and bodes well for both of these Machines.

Well, Having had several SACD Standards, I can say that redbook performance on my 505 is an order of magnitude better than the Standard. Similarly with SACD performance. Same cables, preamp, amp etc. Night and day. They share very few parts. The Physical size difference should also be a clue these are very different machines. Is CAST a 4k retail upgrade? Products that cost 4k more tend to sound very similar to folks who don't have the scratch... I suggest YOU talk to Krell. They tried to talk me out of buying an SACD Standard MK III, knowing I already have a 505. Why do you suppose that is? 'Cause they are the same inside? Please.