1) The USB port on the back of the 990 is the square connector (like the one found on the back of a printer), not the flat one like you see in the back of your computer. The cables you have lying around will work just fine.

2) The 990 ships from the east coast, while the 7500 ships from the west coast. Ground shipping will get you the 990 in a couple or three days. I'd suggest calling Outlaw in the morning and asking them about what your shipping options are for the amp.