Bi-amping vs. bridging

What would the cons be for splitting the front L/R outputs at the preamp to provide the signal into the amp? Is this also an impedance consideration?

I suspect that won’t be a problem in this particular case, although I can’t say that with certainty because the output impedance of the AV-7005 is not specified.

As I mentioned earlier, driving two amplifier channels from the same preamp or prepro output stage will result in the preamp or prepro seeing a load impedance equal to the input impedance of the amp divided by two. Your Rotel RKB-650 amp has a specified input impedance of 20K, so two amp channels in parallel would present a load impedance of 10K. That would be a problem for many tube-based preamps, and for at least a few solid state components, but I suspect it would be ok in this case.

Also, to minimize the cable capacitance that would be seen by the prepro it would be preferable to split the signal using short y-adapter cables connected to the amp inputs, in conjunction with a single RCA cable for each channel, rather than splitting it at the outputs of the prepro and running two RCA cables for each channel. Although given the short lengths of the interconnects that appear to be required in your setup it probably won’t make much if any difference either way.

Regards,
-- Al

... should I be using the Front High or Front Wide for the second channel for the tweets?

I have no experience with av pre/pros, and perhaps someone who does will chime in and address this question. But as I see it what matters, assuming that the goal is accurate behavior of the amp/speaker combination, is simply that the signals provided to the two sections of the speaker (and therefore to the two corresponding channels of the amp) should be identical.

Best of luck with the new speakers! Regards,
-- Al

P.S: Although it probably won’t be an issue, especially if your preamp (or whatever component is driving the amp) is solid state rather than tube-based, a point to be aware of regarding biamping is that since the preamp will be driving two amp channels for each speaker it will see the amp’s input impedance divided by two. Unless, that is, it provides four or more channels, or it is one of the rare two-channel preamp designs which provide two pairs of output jacks for each channel ***and drives each of them with a separate output circuit,*** rather than the much more common approach of simply connecting them together and driving them with the same output circuit. (Asterisks added for emphasis).

Regards,
-- Al

Using an amplifier in bridged mode causes it to "see" a load impedance equal to half of the speaker’s actual impedance. The Motion 20’s nominal impedance of 4 ohms would be seen by a bridged amp as 2 ohms. I doubt that your amp could handle a 2 ohm load with good sonic results. And I wouldn’t be surprised if the amp’s self-protection mechanisms were triggered if it was operated in that condition, causing the amp to shut down.

It might be a different story with the IQ5, which has an 8 ohm nominal impedance. But I suspect that even in that case you would get better sonic results, albeit probably a bit less power, via biamping.

Regards,
-- Al