MrSandman's post got me thinking, so I'll add some of my experience so far with cables, just to keep things rolling. I'll probably add another post in a month or two, as I am beginning to experiment with several brands of interconnects at the moment (trying to decide what to use when I get my 750 as well as tweaking my system overall).

Audio/video interconnects: I used Radio Shack cables for years, back when I had a Pioneer receiver and CD changer. When I added Monster Cable interconnects (Interlink 400 Mk2's) between my Harman/Kardon CD changer and Yamaha receiver, there was a detectable improvement over the old Radio Shack stuff. About two years ago, I had changed over entirely to Monster Cable for audio interconnects, speaker cables, and S-video cables. Recently, I've found a visible improvement in video quality when upgrading from Monster Cable to BetterCables S-Video cables (between a Panasonic A310 DVD player and my Outlaw 1050, and between the Outlaw 1050 and a Mitsubishi 27" direct view TV); I plan to also upgrade the S-Video on my digital cable box and VCR to BetterCables. Improvements caused by upgrades to digital interconnects (coax and optical) from Monster Cable to BetterCables were minimal. The HK CD changer used coax digital to the 1050, with very little benefit obtained by going from Monster to BetterCables (although I preferred the RCA connectors on the BC cable -- they are a solid fit without seeming over-tight). I have used Monster and BetterCables optical (the BetterCables cable is thinner, but has a nicer build quality and performance that seemed identical to me) and a BetterCables coax digital cable on the A310 DVD; the coax seems to have a somewhat warmer sound, but I can't say if it's real or imagined. I replaced the HK CD changer with a Yamaha CDC-775 recently, and began using analog interconnects (the 1050's DAC sounded nicer than the HK FL-8300's, but the Yamaha DAC gave a warmer, cleaner sound than the 1050) -- Monster Interlink 400 Mk2's. I was recently loaned a pair of Magnan Type Vi's, which replaced the I400 Mk2's. The change was absolutely amazing. More and clearer bass signal, as well as clearer mid's and high's. Expensive cables, though, and I am going to be using the CD-to-receiver channel to test several cables soon -- TMC Yellow Label and White Label first (they're on the way from Australia now), but also BetterCables audio interconnects and hopefully Outlaw PCA's. I'll report my findings here.

Speaker cables: Currently, I'm using some old Monster M.75 cables (very heavy stuff) with Tributaries connectors to biwire a Paradigm Studio CC center channel, and Transparent Music Wave Super cables on Studio 60 mains. I went from bi-wiring the Studio 60's with two runs of 12ga Home Depot wire to bi-wiring with the Monster M.75 on the low freq and the 12ga Home Depot, and found an immediate improvement in low end. The Transparents are not bi-wired (have very short jumpers at the speakers), but when they were added, the improvement in sound was startling -- more bass, clear bass, and much clearer and pronounced mid-range and high frequency. I tried bi-wiring using the Transparents on the low freq and using both BetterCables premium speaker cable and Monster M.75 on the high freq, but in both cases the Transparent ran roughshod over the other cables. Once I get a Model 750, I'm going to experiment a bit more with speaker cables (try my pair of BetterCables speaker cable on the center channel, and I may try to get a pair of TMC speaker cables to experiment with on the center or even the mains).