Opinions

I would not buy them at all but put the $$ into an EITR, an optical isolator or a better DAC.

If I were forced to buy cables, I'd try out the Lush which a lot of people like (no real listening tests on them tho).

I would always address the problematic USB interface and the speaker cables before mucking about with interconnects, which should be balanced anyway.

My experience is to use higher quality interconnects at the source component.

I see. Usually at the source, yeah, but you would have to experiment. And I would certainly maintain one brand approach.

I think your biggest concern is which interconnect to buy that will work best for your tastes and in your system.  It would be helpful to know what interconnects you're using now and what you're areas you're looking to improve upon and you'll likely get some good recommendations here.  Once you choose you can try it in both positions and then it's up to you regardless of what we say here.