I am on the verge of buying a miniDSP-HD, or more accurately, the DDRC-24 version as it includes Dirac 3.0 functionality.
That unit is overblown, as it includes pointless analogue inputs, but it would be cool if HiFiBerry could make a better version, digital input only, direct from the Pi, and with improved quality DAC outputs (like say DAC-HD quality or better). It'd need an optional Dirac license and a calibrated mike, and so will be expensive. But it could move HiFiBerry from "cheap and cheerful" to actual "HiFi" auto-equalized for your room and speakers, including your subs (it has 4 outputs).
At the moment, miniDSP has no real competition... And I'd rather buy from HiFiBerry where possible....
