What seperates "hi-fi" from "mid-fi" in cdp's?

Robust power supply, top-shelve analog stage, I/V stage, transport made out of metal with delrin or high-grade nylon gears (not plastic), double-sided epoxy PCBs, attention to EFI/EMI shielding, quadeutectic solder, superior circuit board design and layout and ULTIMATELY sound quality.

LMAO Nrchy!! Absolutely agree, listen to the gear in your own system...is your foot tapping involuntarily...well then see a doctor....do the hairs at the back of your neck stand up...you may need a trim, the barber's the one for that....

Great advice too about the older technology units. I would not necessarily limit your search to upsampling DAC's though. Some of the very best DAC's are straight redbook with no upsampling. Unless you have to hear what SACD sounds like, it should not be a criteria to seek out as the selection is pretty limited right now (in terms of music released on SACD) and no one seems to know whether it will live or die as a medium. There are certainly players that do both pretty darn good as I understand it.

Let your own two ears be the judge...good advice that goes much further than CDP's in this hobby, yet is so often ignored.

Marco

all the subtle, but important differences! Like the difference between a Shaolin monk and a heavyweight boxer (like someone mentioned in another thread).

I imagine after living with a high-end source for a while, it would be tough to go back to a mid-fi one and still be satisifed with it. The inverse, someone who was used to mid-fi might hear a high-end source and be left wondering what all of the fuss was about.

Richard Hardesty's issue #9 of the Audio Perfectionist Journal has a really, really good article about this very subject(some of it might be surprising)
They're some really good low priced players on the market and some of the really expensive ones are more smoke and mirrors than an improvement. It is no doubt that some players are built to much higher standards even though they might not sound better. The type of DAC they use, the power supply and shielding, etc come into play.
At this point in the game, I would look for a SACD player that is good with cd's. Most newer CD's will be hybrids w/SACD layers. SACD sounds better with most recordings even own cheaper machines. The Sony 9000ES is an exellent example used(including a decent job on CD and plays superb DVD)and is a really good SACD player.
I have no experience with DVD Audio so I won't comment on that subject.
I use a Meridian 508-24 because IMO, it has less of a "Digital" sound and doesn't give up anything in resolution. It only weighs about 13# but it is extremely well designed. I have a excellent sounding NAD 1- bit player that, in comparison to the Meridian, misses a few small details but doesn't add crap to the sound. If you hadn't heard the Meridian, it would be satisfactory. The difference in price is $3995 for the Meridian and $599 for the NAD!
The point being, as some others pointed out, it's in what you perceive as significant for sound quality. Go listen and decide for yourself. Not everybody cares about the last nth degree of resolution. In the CD world , sometimes its just better to have a smooth, non-fatiguing player.
With all that said, the dividing line has become cloudy between midfi and hifi players(based on price). Most all are decent now and differences are in construction and ultimate resolution with the biggest difference being brand name recognition. The limiting factor now, IMO, is the CD itself and has been for sometime. Of course certain CD's are better produced than others and when you run across one, it can be a real treat!

Your ears matter. Everything else should be treated as marketing. That's not to say that a 24 bit DAC is better or worse than an 18bit DAC, but who the hell cares what DAC chip a player uses if it sounds terrible to your ears in your system.
I'd short list 4-5 players that receive good reviews then listen to them and see if one stands out.

Trying to select based on specs would be like selecting a sports car based on the number of cylinders, or whether its a pushrod or an overhead cam. In the end you have to drive it to find out.