Mixing and Matching Cable Brands: Bad Idea??

I've wondered if there is anything scientific to some claims that different brands of cable, when installed in the same system, can "work against" each other. Is there any truth to this?

I've flipped around different brand cables from front end to back end and never got the results I wanted. I recently threw out my patchwork of copper and started over with same brand ICs and speaker cables. The results were dramatically better. And it's not as if i made a huge upgrade. The move was relatively lateral. What's your experience?

Thanx in advance.
Greg