You can easily get away with 180 dpi at final size on an Epson 7800. While 360 dpi is the "native" resolution of the printer, you don't really need all that to have great prints. I have both a 9800 and a 9900 and have made many large prints at 180-200 dpi and have never been dissatisfied, even at close examination. The problem here is, of course, is that your film doesn't hold more than 1600-2000 dpi worth of information, so scanning it higher just accentuates the grain. Did you say what kind of scanner you're using that can actually give you 7000 dpi or is that an interpolated number? If it's any sort of CCD scanner, where you don't have aperture control, you may indeed have better results scanning at the aforementioned 1600-2000 and then rezzing up as needed. The other thing we haven't discussed is using something like Noise Ninja on film, which actually works pretty well and was the reason I first bought that product six or seven years ago.