Unequal length interconnects?

I recently acquired a second Monarchy SM-70 Pro, and with the power distribution in my room it made sense to move both amps out of my rack to under the speakers. I got upgraded power cords (Volex 17604s) and a pair of 4ft Speltz Anti-cables to my Von Schweikert VR-1s, both of which made an audible improvement.

The last piece of the puzzle is the interconnects from my Wright WLA12A to the Monarchys. In my current room the rack needs to be in the corner rather than between the speakers. The distance to the far amp is about 12 feet, with the near amp at about 4 feet. I had two 6 foot mid-level Calrad pairs (http://www.electroniccity.com/shopping/pricelist.asp?prid=498&brandinc=42)
so I split them up and used a decent quality F-to-F joiner to make a 12 footer. I tried it with 12 footers on both channels and with a 12 footer to the far amp and a 6 footer to the near one and could hear no difference.

My questions are:

1) Would there be a big improvement using one solid 12 footer versus using the joined 6 footers? Right now I have no way to test that, so I was looking for someone who may have tried it.

2) Is there any downside to using unequal length cables? If I get two 12 footers I'd have to do something with the excess on the near amp.

In either case, if I have to replace the Calrads I'd probably go with something like Signal Cables, which would probably be a step up anyway.

Thanks for your help.

David