Hi Nash, The good news is that these CNC Routers will indeed machine aluminium.
In fact member " Blunderbum " has recently taken delivery of his Excitech and is using it for a similar purpose to yourself. He has posted a photo of a n Exhaust Flange cut from 8mm thick alloy.
You can look at his thread in this section of the forum ( Excitech ) in a thread titled " DSP Question " Post no.16 has the photo.
Also check out the videos on Youtube - just type in Excitech CNC Router
and you will see some machines cutting Aluminium.