Overcloking SGDMA transfer using clock crossing bridge

If that SRAM is not synchronous (not SSRAM) I wouldn't expect too much more performance out of it.

Assuming you are using SSRAM then you would probably want the clock crossing bridge to be between the DMA masters and the on chip memory if you want to put the SSRAM and DMA on a different clock domain. This will make sure SOPC Builder doesn't insert a clock crossing adapter for you which only handles a read every 9 clock cycles approximately.