So long as a system has:
1) rock solid connections at all points that are cleaned on a somewhat regular basis
2) cable that does not saturate under load ( i.e. too small of a gauge )
3) cable that doesn't introduces any type of series resistance to the circuit
4) cable that is not highly reactive ( inductive or capacitive )
everything should be fine and pretty straightforward to deal with.
Just as the situation gets more "specialized" or "out of the ordinary", so do the installation requirements. There are some circumstances that a "less than stellar" set of speaker cables can actually out-perform "hi-end" cables, etc.. These typically fall into the "high reactance" /"freak" speaker load category though. Having to resort to this type of installation though is a sign to me that something, probably the amp, is not up to dealing with the load ( speakers ) that it sees and the "junky" cables act as a "buffer".
The biggest problem with people trying to use "heavy wire" to keep resistance down to a minimum and pass a maximum amount of information is that they typically resort to some type of "monster sized" zip cord or other cables with high inductance. High inductance speaker cables resort in rolled off upper mids and treble, lack of detail, loss of air, weak harmonic structure, etc...
Since longer cables would have higher levels of inductance, increased length would only compound the problems that i mentioned. In a situation such as that described, there would be obvious benefits to keeping the speaker cables ( and the inductance ) as short and as low as possible.
In order to avoid that type of pitfall, folks should look for speaker cables that are of a heavy gauge but make use of "fancy geometries" in order to minimize reactance. Another "side benefit" to these "fancy geometries" is that they are typically less prone to acting like an antenna, picking up emi / rfi, etc... Obviously some geometries are going to work better than others and the trick is knowing which is which. I've seen MANY factory designs that are operating WAY below optimum. Reconfiguring the cables and reterminating will typically show marked performance improvements that are audible as well as measurable. I'm not naming names though as i don't need any more hate email or threats regarding lawsuits.
As to your specific installation Ernie, I see no problem with how you set things up so long as the amps are not tucked up into the rafters. They obviously need some room above them to help dissipate the heat / let the heat rise. The fact that you are running balanced negates much of the negativity of my comments ( is that a double negative then ?? ). This is proven by the fact that you have minimal noise even though you are running in close proximity to known sources of emi and rfi. If you would have used RCA's in that installation, i would venture to say that you would have had much poorer results.
On that note, i have to add that not every installation or system can be done "optimally". I myself am running long ic's ( 12 foot ) and short speaker cables ( 4 foot of 7 gauge ). As you might have guessed, i did this because i'm running monoblocks and have them perched behind the speakers. To top it off, the ic's are single ended ( twisted pair of wire with RCA's ) and NOT balanced. The preamp that i chose to use there is fully capable of driving VERY long cables though, as i checked into that right off the bat. Unfortunatly, it does not have balanced outputs or i would be using them. Like anything else though, it is a balancing act. I feel that i have lost some detail by using the longer IC's but i've gained better control of the driver courtesy of the shorter speaker cables. Such is life.... Sean
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