Spkr Cables . Can you use 2 diff brands at once?

Tie one end of the short cable to a stop sign the other end to the bumper of your vehicle. Now just pull the car forward, problem solved. I'm good :^)

Don't waste your time. I had TARA Labs/XLO Reference on my B+W 802's because a store in SF had the same thing. Stick to one brand.

Not for R-L but you could get away with using different speaker cable for the bass/midrange section. You should have equal lengths on both sides.

Even if they cables are the same type, they really should be the same length. This is so that the loading on the two amplifier channels is the same.

As for mixing and matching: If you are on a budget, then using one for the treble and the other for the bass can be synergistic depending on the system.

There are two philosophies surfing arround this area:
One of them CABLES DO MAKE A DIFFERENCE and
the other CABLES DO NOT MAKE A DIFFERENCE.

If you believe into the second philosophy than it doesn't matter. Zipcord is fine all the way through without any research and spending money for AudioQuest or Kimber.
If you believe in to the first than you should have cables of the same brand preferably even of the same length if such possible or the length difference must be minimal.

As far as I understand to sell just only one speaker cable is much more difficult than to sell a pair of equal-length speaker cables.

P.S. You can use different brands at once per one channel when you biwire or biamp.