Why not replace your current panels with new ones? If you can generate nearly 3 times as much electricity with the same roof footprint and be able to reuse your racks and electrical installation, you should be able to be in the black in no time.
I am already "in the black" as it were since the system has already provided more value than it cost to install and maintain. So no worries there. But 325W panels are physically larger than 185W panels (not twice as large but still) so replacing the 28 panels on the roof with them would get my raw input up to 9.1kW but I'd need roughly 33% more surface area. That would add another strut on the mounting system and the top row of panels would extend beyond the peak of the roof (now disallowed by the building code). However, it would be "easy" get get 16 in there, which would be an equivalent raw foot print (5,200 watts)
