The Benchmark and Bel Canto are excellent DACs at their price points, but they are not at the very top echelon of performance.
The subject of this thread is Wadia with Benchmark. There's much evidence here that this combination will not be superior to a good stand alone CD player
I think the question was actually what transport to hook up to DAC1 and if there are any differences. The answer seems to be that DAC1 sound is independent of transport & cable & digital input provided the "bits" arriving at the DAC1 are the same (at least many people report this and it is what Benchmark vehemently claim).
Now what "sounds" better or best is, IMHO, a whole other can of worms, which includes the subjective preference of the listener. Certainly a different D to A converter and analog output stage of another high end CDP (removing DAC1 from circuit) is going to sound slightly different - just the same as different DACs will sound slightly different.
Subjective sound preference is hardly "evidence" in the same sense that test results made on the Benchmark DAC1 demonstrate it to be jitter immune and hence transport & digital cable independent (provided there is bit transparency). Note that DAC1 test results say nothing about subjective sound quality - the DAC1 while transport independent may sound terrible to some people. My advice would be to simply listen yourself and buy something more "top echelon" in that case.