Speaker cable length

I have exactly the setup that you are planning on. Keep the Left & Right the same length, it matters. That's just physics. Now people can argue they can't hear the difference but they are talking about their own hearing and not the laws of physics. Of course with that setup you are going to have on the one side a lot more cable to hide (or manage) than the other side.
For this reason alone opt for quality solid core cables that are easier to handle. Your ears will thank you as well with superior sound. Check out DNM's range and pick something you can afford. when looking at their products don't think that the cable's are specific for their amplifiers etc. That certainly true that they are designed in conjunction with everything else but they are tremendous in my setup.
Good luck with this.

Same length and not more than 10 ft after that the sound starts to degrade

Thus is controversial topic and I have heard all sorts of statements. What seems to be consistent at its base (I'm going to ignore brand names and technology to keep this less controversial) is that length of cable and Guage of cable matter. I dont have any hard numbers to contribute but for longer distances let's say 25ft the wire Guage should be higher ie 12AWG. I dont have a sense of low distance and what Guage you can get away with. Theoretically if its a 3ft run the Guage shouldn't matter that much. In audiophile land however I'm sure everything matters and so opinions will be hot on this.

 I keep it really simple and go with monoprice 12awg. I buy terminal plugs and make my own lengths. This might cost you $70-80 or less to make a 100ft run if you chose. Once you get into branding and technologies however the arguments explode. I do know people with monos will argue for shortest length possible as one of the advantages is to be able to place your monoblock right next to the speaker. Ultimately if someone is building a system it seems most prudent to spend the money on the best components and treat wire as the final thought to save up on if one so chose. Otherwise 12 awg from any brand with your own terminal plugs is great. 

Some of you are delusional.   There is no rule on speaker cable length.  Unless you were gifted with God’s ears, you can’t hear a difference from a 4 foot pair of cables and a 20 foot pair.  If you think or believe you can, you can’t. The electrons will arrive at the same time regardless the length as long as the wire gauge supports longer runs.  Do you think the recording studios use short cables?   Think again.  

@stereo5 that's what I'm inclined to believe. I mean, we're talking speed of light here, and unless you're running really thin 18 or 20 gauge wire, our ears just aren't good enough to pick up any difference. Especially with signal strength as low as what's conveyed through speaker wire.