Speaker wire selection for inefficient speaker?

This is a good question. Center channels carry a huge percent of movie content. Make sure the tweeter of your center is the same height from the floor as your L-R channels so they are all on the same plane. Next, use a sound pressure meter and run the test tones from your receiver, is the volume the same in all front channels? Do you have to boost it? If you are using the same cable on your other speakers it shouldn't matter.

Cables will not make a difference. I agree with @fuzztone. You rebalance your surround processor. It will do the job for you. You go through an cycle to set volumes and delay times.

To answer Kota, I have a receiver with tone control, and an external amp. When I run tone test check, Center is always the lowest and needs +5 dB increase to level out with my left and right channels (B&W 805), hence trying to help it a little but as I assumed and others stated, a wire that short shouldn't matter in terms of resistance. 

@alexb76 , its fine to boost the center, that is why the receiver has that feature. If you want to change speaker wire do an upgrade for all of your speakers, Having said that I doubt the wire is whats causing the volume difference. I would just boost the center like you have and leave it.

A little perspective.  90+% of the problems are associated with too small a gauge wire. This is especially important for inefficient speakers.  So I always use 10awg wire for speaker wires.  From there you can spend thousands of dollars on the last few percent but the key is heavy gauge.