Any Audio Grade Extension Cords???

I thought everything was all planned out with my new audio cabinet (custom built wood) but alas, I find my tuner needs to be located well away from my pre-amp -- about 6 feet. I've got some good rca cable to connect the two but my built-in power cord for my tuner needs to be about 4-5 feet longer to reach my power supply. Does anyone have experience with audiophile extension cords? Is there such a thing? Does it even matter when the rest of the cord going to the tuner is stock Marantz (no IEC)? Thanks in advance.