nfaguys,

I've got to admit that I'm not a true believer when it comes to the benefits of exotic (and expensive!) cables. That said, I do use good quality cables (speaker, XLR, analog, digital, etc) including ones I have made myself. In the past I noticed significant improvements when using good cables over cheap (small gauge and poor shielding) ones but beyond that IMO the benefits are marginal at best. For digital and analog RCA cables I use cable and connectors that are both 75 ohm. Analog connectors can be made with 50 ohm connectors but they will not work with digital signals. I'd look for cables made with Canare, Belden and Permaseal products. All are quality (e.g. Bluejean uses Canare) products that will provide excellent results.

Speaker wire gauge should be based upon the length of the run and the impedance of your speakers. A quick google search should yield a table to help select speaker wire gauge. I use 14ga in-wall wire for runs less than 50 feet and it works well.

The choice of whether to connect a CD player via digital or analog probably should be based upon the DAC's in the CD player versus those in the 990. I have connected my CD player to the 990 with both and I like the 990's DACs better. With the digital connection I'm able to take advantage of the upsampling stereo mode which I prefer. A 75ohm RCA cable (or optical) is all it takes.