Bi - Amping

... what are the consequence or disadvantages of not using the same Amplifiers ?

Assuming you are referring to passive biamping (i.e., without using a crossover device between the preamp and the power amps) the advantages and disadvantages include the following:

Advantages:

1) A modest increase in maximum power capability, perhaps just 2 db or thereabouts depending on the speaker’s internal crossover point and crossover slope and on the power capabilities of the two amps. Not sure how helpful that would be, not only because the difference is small but also because all four of the amps you mentioned (one of which is an integrated) are fairly powerful.

2) Possible improvement in the sonics of each amplifier, since it would only have to provide current and power in part of the frequency range.

Disadvantages:

1) As George indicated you would have to provide a means of matching the gains of the two amps, such as the device he suggested.

2) Increased loading of the preamp, i.e., the preamp will see the combined input impedances of the two amps (in combination also with the impedance of the Sys or other gain matching device), which will be much less than either of the individual impedances of the amps. Depending on the design of the preamp that stands a very good chance of applying even though you would be using RCA outputs to one amp and XLR outputs to the other. Many and probably most such designs supply the same signal to their RCA output connectors that is supplied to one of the two signal pins on the XLR output connector for the corresponding channel. That may or may not be a problem depending on the output impedance of the preamp, on how that output impedance varies over the frequency range, and on the input impedances of the amps and the gain matching device.

3) Possible loss of coherence in the presentation, due to the two amps having differing sonic characters.

4) The need for additional cabling.

5) Increased potential for ground loop issues.

The bottom line IMO: It’s probably not worth doing. It will make a difference, but not necessarily for the better.

Regards,
-- Al

lordrootman OP

Halo A21+ on the mids and highs, because it’s "high bias Class A/AB operation" John Curl design, which will be better for the mids and highs.
And probably the Anthem ( Sixteen bipolar output devices per channel ) on the bass for the current in can deliver into 2ohms

And the Rotel Michi having 100ohm output impedance will have no trouble driving any combinations of amps you have

To me if you have the amps, it’s well worth doing as it will cost next to nothing to do and you’ll gain from it.

Cheers George.

Ensure that the gain on the different amplifiers are the same. 

Ensure that the gain on the different amplifiers are the same.

They won't be, and that's what the $49 Schiit Sys passive is for.

Cheers George