With regards to surround sound I am not really sure; I would think that you simply connect your HDMI cable to your sound system and select "HDMI Raw" for audio selection on the PBO Alpine. You will need an HDMI output out of your sound system to your television for this to work; not all sound system offer such an output (HDMI). As far as other firmware, nothing that I know of right now but the PBO Alpine uses the skyviia SV8660 processor and many other players uses the same one so it is possible that some of those other player's firmware works with the PBO Alpine ???? For now I just prefer to see what PM may have to offer with regards to the matrix firmware. This firmware source code is suppose to be eventually release which will make it easier to improve upon ..... well maybe. .
Sorry this is all the help/info I have right now.