XLR cables for high-end multichannel system

I'll third the recommendations of Mogami Gold Studio, especially given that you don't yet have a finalized set of components in place. Whether or not the cables you select will behave in a "fairly neutral manner" depends to a significant degree on the impedance and other technical characteristics of what they are connecting. So I think that making a major investment in cables at this point would be premature.

Based on both anecdotal reports I've seen in the past and on technical considerations, IF the Mogami's were to deviate from neutrality to a perceptible degree with the components you end up selecting it would probably be in the direction of providing a slightly more relaxed, non-aggressive presentation than is typical of many of the more expensive cables.

Also, keep in mind that cable differences will typically be less pronounced for balanced (XLR) interfaces than for unbalanced (RCA) interfaces.

Regards,
-- Al

Would the Mogami Gold be a significant upgrade from the Blue Jeans cables, at least at this stage until my system is complete?

If the Blue Jeans cables are the ones that utilize Canare L-4E6S, I would not expect much if any difference.

If they are the ones that utilize Belden 1800F, the Mogami has significantly higher capacitance but significantly better noise rejection. That would include rejection of noise at ultrasonic and RF frequencies which may not be directly audible as noise, but may have audible consequences due to intermodulation effects. Although the balanced input circuits of the amplifier presumably should cancel most such noise anyway.

The higher capacitance of the Mogami, compared to the Belden 1800F, may result in a very slightly more relaxed upper treble, if driven by the 500 ohm or so output impedances of the Onkyo and the DSPre. The magnitude of the difference will increase in proportion to the length of the cables.

Other differences, if any, are probably not predictable.

Regards,
-- Al