The wire inside the speaker cab matters very little, not because stick-in-the-mud, flat-earth, fuddyduddies say so, but because:
- It's SHORT. Whatever effects a cable has on the signal, the effects are magnified by length. The tiny bit of wire inside a cab isn't enough to mess up the sound, even if the wire is crappy.
- It has ZERO capacitance. Capactance is what kills highs in audio cables. It's caused by the construction of the cable; two conductors in close proximity separated by an insulator. The longer the cable, the higher the capacitance (See #1.) Speaker wires inside cabs are single conductors, bascially flying leads in air. Since they are so widely separated, they don't even "see" each other to interact, so no capacitance.
- The current it needs to carry is TINY. Let's look at the worst case: call it 100 watts into a 4-ohm cabinet. Work through Ohm's law, and that comes out to 5 amps of very intermittent current flow. If you go look at current ratings for wire, you'll see that #16 is rated for something like 10 amps, #14 is good for 15 amps, #12 for 20 amps. Keep in mind these ratings are for real-world applications: wires run through conduits carying power to continuous loads, extensions cords covered in heavy insulation powering tools, Romex cable run through walls connected to lights that are on continuously for hours at a time. Wire current ratings are designed so that the current can flow and the wire won't heat up to the point where it causes a hazard. So, that #14 Romex runnig through your walls can handle a LOT more current than its rated 15 amps, but it's specified extremely conservatively. In your speaker cabinet application, the wires are hanging in free air, with much less chance of heating up. So let's see... #18 is conservatively rated to handle TWICE the current your speakers need. (In free air, it can probably handle 3 or 4 times.) #14 is rated for three times what you need, #12 is rated for FOUR times. Remember, these ratings are for real-world lengths, too; you're running a couple feet of wire at most. The point is, no matter what wire you put in there (as long as it's not stupid-skinny), it is WAY overkill. You're simply not going to hear the difference between 2x overkill and 4x overkill.
I say, go to Lowe's or Home Depot. Ask for some type THHN #16, which they sell by the foot in a variety of colors off that big motorized rotating rack thingie. Make sure you get the stranded variety, as it might be availabe solid, as well. Pick two colors so you can keep your (+) and your (-) straight. #16 is, as I said, overkill, but it's still small enough that you can solder it with a halfway normal-sized iron. If you want to get fancy, you can use crimp-on lugs that match your speakers.
You really don't need anything more expensive; it's all snake oil.
