All single element in the path is important, but DAC as "the source" has tremendous importance.
1) DAC converter (chips) is important: there are many types, but IMHO only 2 groups: old plain multibit, and sound processing delta-sigma/single bit. IMHO multibit are way better, and old and cheap chip like TDA1543, or not so cheap but quite old PCM1704 could easily beat the newest and "the best" sigma-delta.
2) Existance (or not) of oversampling (digital filtering). IMHO non overampling (NOS) it way better.
3) Type of I/V converter: active or passive (passive is simpler to be implemented in proper way).
4) Existance of analogue filter. Very simple or not a filter at all is better.
5) Existence of op-amps and how many of them. IMHO no-op-amp solution is the best, because every one op-amp is overcomplicated net of transistors, which behave in unpredictable way with the real dynamic acoustic signal.
6) Clock should be stable, because weight of every sample depends on digital value of the sample and width of... clock tick.
7) Power supply, path of the mass at the PCB, quality of the resistors, existance of capacitors in the path - all aspects are important.
Edited by borizm - 2/6/12 at 10:01am