well if you get the 2ohm SWS-8 you'll get 100W from each channel on the XD
which is a better option because your front and rear speakers are rated at 2ohm (so they will be getting 100w anyway)
so i'd prefer to give them all the same wattage
not 100 front and 100 rear but only 75 to the subs
i bought an Xd600 but i haven't had time to install it yet, still sitting in my trunk in the box
but i liked the option of having stereo bass
and yes i know that bass is non directional , but it still makes me feel better to know its stereo