Greg,
The inverter that does both grid tie and independant AC power output is called a 'multi-function' inverter. They connect to battery pack, PV array, PoCo, AC load, and standby generator. Basically they are everything in one box. I believe Trace is one brand, there are probably others.
I believe battery pack voltage and PV output voltage have to be the same. Therefore the PV array will dictate battery pack voltage. Lead acid batteries are not the best as far as storage efficiency but they can be significantly cheaper. If possible, use deep cycle batteries because they have better grids for the lead to plate back onto. You may also have to check with the local fire department if a significant amount of sulphuric acid is going to be onsite.
Larry
