Mixed-signal modular system GND scheme question ?

[intel386]

Hi,

I'm attempting to create a sensitive mixed signal system (24 bit or more audio) compose of a backplane and stacked modules on 2.54mm headers.It is multi-channel and channel's modules are well separated with independent supplies of their own.
The only common module is the DSP, therefore all separate GNDs of all modules will meet at a single point is the DSP's supply GND.

My questions are :

Please take a look and see if there is any problem with my wiring ( quick draft attached below ), both in DC and low-freq noise ( shared impedances in GND return paths ) and HF, spiked noise ( digital and analog return flows ) ?

Is there any advice/caution regarding making a system on backplane ? The 2.54mm hdrs are good enough for 50-100MHz signal ? Any caution making connection through these tiny pins, especially with GND involved ? Should I treat the BCKPLN as a board of wires and traces only, or make use of it's copper planes for some further benefits ?

Thanks 

Here is a quick draft of system wiring :