Congratulations on the Makua!Sweet... and what a coincidence! And I am told the Makua with the DAC card built tin actually sounds a wee bit better as the need for yet one more set of interconnects is left out of the chain.
I'm a big believer in eliminating cables when possible. Since my setup is so simple (1 digital input), adding a Makua wouldn't be the best use of my audio budget even though I'm very curious about the musical qualities the Makua might bring. A photo of the Makua + Kalugas brought on severe audio lust when they were first released years ago So, the Makua has resided in my brain for some time...
Haven't tried using the MU1's volume control and running the Tambaqui full tilt to the amps. That might be interesting. Grimm has introduced a MU2 (will be sold in October), which is a MU1 streamer + DAC + analog volume control in one box. Again, considering what eliminating a cable (not to mention fine tuning the DAC for the streamer output) as well as an analog volume control might bring, has me curious about that option too.
Did you get the Sonore upgrade yet?