Quality review of Belden 8473

Cables are cables. Belden happens to make some of the more durable products on the market, but cables don't affect sound quality. Invest your money in other things, and spend less on cables when possible. In this case just buy something rated for outdoor use that's 14 gauge and be done with it.

Video has a much higher bandwidth requirement. But once your cable is sufficient, you can't get better video performance from a "better" cable.

As far as audio quality is concerned, cables can be detrimental, but once you have a cable that is both sufficient and transparent, you can't improve upon it.

In either case, audio or video, you can't make something out of nothing.

Belden 8473 uses PVC for insulation purposes. PVC can be formulated so that it is quite flexible and reasonably durable. Its durability and longevity though with respect to direct exposure to the sun and other outside elements is a function on how it's formulated. By that I mean factors like the molecular weight of PVC, the type and quantity of plasticizer (that's what makes it supple), what fillers are added (whether they're stable to sunlight - UV stable) have a direct impact on where it can be used. You could always contact Belden directly to see if the 8473 is suitable. They do have toll-free numbers where you can speak to an application engineer. Another company that may have what you're looking for would be Liberty Cable.

Generally speaking, and I do mean generally, the majority of speaker wires that are PVC based would not be recommended for this sort of application because heat and UV exposure will cause the insulation to break down. Instead, what many do is choose something like low voltage wiring which is available in many home improvement stores. This is the sort of wire that you'll find that powers many outdoor lights.

As to your concerns about someday in the future getting 'better' equipment than you presently have I wouldn't worry too much about it. Better equipment does not tax any speaker wire of suitable gauge. Now, you might want the wire to look nice when it's indoors, but that's another kettle of fish.