Every single CD player from the beginning had to use buffer between the optical reader and the dac. The data is in interleaved form on the disc and you have to buffer it to decode.
True, very "short" FIFO only (512K). When it comes to 64MB (or more) SDRAM buffering, the CD player has to spin at x4 minimum. And that is what works best, IMO!
Josh is correct, it does not really matter whether the entire CD will be recorded to memory, or it will be partially recorded to memory, the result/benefit is the same.
Now, the computer based solutions do not only feature a very noisy switching power supply, but also are using the highest read speed transferring the CD to the memory. In my opinion, this is inferior to designs partially buffering to memory while spinning the disc at lower speed.
Regards,
Alex