a. Just know it can cause some cancellation issues and actually hurt things.
b. Running one channel in 4 ohms is usually no problem for most AVR's that don't claim to work with 4 ohm speakers, but if your AVR / AMP doesn't specifically state it is ok, you are certainly running at least a great risk of failure on the channel.
what do you mean. I have a 1014 it could handle the load couldnt it? How much improvement did you notice. ( not much, some, decent amount, great improvement)? the reason I ask is because ive noticed that depending on the placement it provides different effects. top placement exaggerates high picture sounds. Bottom exaggerates low picture sounds.
Does the 1014 state it works with 4 ohm speaker loads? If so, you run no greater risk of failure. If not you are definetly adding some risk, but as I said most AVR's wouldn't even really know if only 1 channel was 4 ohms.
They list impeadence as nominal because at different frequncies the impeadence is actually very different as in even an 8 ohm speaker probably hits 4 ohms or even less often. But then again if your starting at 4 ohms, it will dip down below 2 ohms at certain frequncies.
Best of luck with it, if you do try it, come back and post up your results.