DAC/Pre-Amp Upgrade, R2R or Delta Sigma?

Global difference in sound signature, not sure what that means. As long as a DAC's noise and distortion is somewhere around - 120 there isn't going to be much of a noticable difference. The thing is R2R DACs  tend to not measure well so some will roll off the highs and produce noticable distortion which I imagine is where their " sound signature " would come in. There are of course lousy implemented Delta Sigma DACs too but a well implemented one like a Benchmark DAC3 doesn't really have a sound signature it's considered very neutral so what' goes in is what comes out. Good recordings sound good bad ones bad. Try to narrow down to a couple and get a friend to switch them back and forth and pick the one that sounds better to you using only your ears not your eyes. 

I probably should have just said using my ears instead of my eyes have saved me a few $$$ and at least to me DACs have gotten to the point it's really hard to tell them apart unless they're really bad or try to sound different with tubes or something.