The mechanical part of today's transport is not really important. Two-channel CD, SACD or DVD-A has very little bandwidth compared to the capabilities of super-fast optical readers. What's good for a computer is more than good enough for audio.
Most DVD players buffer many seconds of data and have sufficient time to check for errors and even re-read the same data if needed. That's proven technology that existed 10 years ago in portable CD players.
Power supply noise is not high enough to cause an error in the recovery of the data from the read channel or flip digital 1's and 0's, but it could affect the noise level of the local clock circuit.
The real important factors for a good transport are clock noise level and data synchronization. Clock accuracy by itself is not improtant at all compared to the clock noise characteristics.
On the receiving side, the embedded clock signal is used for two purposes: timing the incoming digital data (not awfully critical) and for recovering the sample rate clock. The latter affects the timing precision of the generated analog signal, which translates to phase and pitch distortion.
The other important aspect in a transport is what it does with the recovered bits from the optical media. That's where the concept of "bit accurate" data stream prevails. The cheap units most likely just clock the recovered data with no alterations, which is the best from the perspective of fidelity to the source. I have a feeling that some units actually process the data and that's where it can get nasty. Upsamplers definietly alter the data, either by adding dithering for psychoacoustic effects or merely by errors due to lack of computational precision. Some may apply filtering to "fix" the data stream for you... Beware of "free" gifts...
My experience with cheap DVD players has been a hit and miss. For some time I actually enjoyed a dirt cheap unit which went on sale for $19.99 at Fry's... and did a great job!
I installed a shielded power cord but othertwise it was a stock unit. It served me real well for 3-4 years until the mechanical transport beat the dust and no replacement drives were available...
Recently I run a Zenith DVB-318 with good results (might be discontinued now) and the Oppo at the San Jose meet sounded really good. All these transports are not "good for the price". They are just good!
