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

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.

I have read several reviews of the 505 where the writers say it is the "best" player they have heard. Can this be done with a new transport and a new clock? C'mon guys. Following this logic the OPs 300 is better than both! Perhaps I should search out some KSAs and ditch my FPBs?

My 505 has two toroidal transformers. A true upgrade for the new drive. Krell did much more than slap a new transport in the mountain of broken Standards piling up at the shop. Eliminating an upgrade path is not typical Krell either. Don't get me wrong, I miss my Standard and will acquire one, completing my KAV stack. For critical listening, I will fire up my EVO. If they sound the same, I'll GIVE you whichever one you want. How's that.