Not sure that there are any hard and fast answers to this one. In my experience, different USB cables made little (if any) appreciable difference in my system. This may be DAC-dependant, and differ depending on the tech they use in the USB interface (I'm on the receiving end of the asynchronus tech developed by Wavelength as licensed to and employed in an Ayre QB-9). I've read that this tech may be more ambivalent to differing grades of USB cable. That's been my experience, but haven't explored at great length and there's no saying (at least not by me) whether this translates at all to other DACs.
Generally, though, Mini-as-transport can certainly punch with the big boys, no matter how you shake it. That said, absolutely correct that there is a whole lot that can be tweaked and improved. Out-of-the-box, plug-and-play, I don't think one should expect a Mini to blow the doors off. But with some care and tweaking, they're no joke.
Oh, and one more thing: don't rule out high-rez stuff yet. I've just begun to experiment with genuine high-rez stuff (with the correct output rate adjusted so that it's run native from the mini to the DAC), and it can be pretty darn impressive. Don't have an opinion about upsampling (other than I don't do it, I try to make sure things are run native into the DAC), but a well recorded high-rez track (the most I have currently is 24/88, but the Ayre will run up to 24/196, I think) is really much better than standard redbook. I'm far from an expert, not even a particularly well educated enthusiast yet, but I have been very, very impressed by the little I've gotten my hands on.
Generally, though, Mini-as-transport can certainly punch with the big boys, no matter how you shake it. That said, absolutely correct that there is a whole lot that can be tweaked and improved. Out-of-the-box, plug-and-play, I don't think one should expect a Mini to blow the doors off. But with some care and tweaking, they're no joke.
Oh, and one more thing: don't rule out high-rez stuff yet. I've just begun to experiment with genuine high-rez stuff (with the correct output rate adjusted so that it's run native from the mini to the DAC), and it can be pretty darn impressive. Don't have an opinion about upsampling (other than I don't do it, I try to make sure things are run native into the DAC), but a well recorded high-rez track (the most I have currently is 24/88, but the Ayre will run up to 24/196, I think) is really much better than standard redbook. I'm far from an expert, not even a particularly well educated enthusiast yet, but I have been very, very impressed by the little I've gotten my hands on.