I realise that you didn't ask about it, but there is always the conversion route. I used Life Pixel for my filter. The advantage is that auto focus, exposure metering, and the view finder all still work, and you don't need to always mount it on a tripod. The disadvantage of course is your camera becomes dedicated IR. I did a Canon 10D that wasn't worth much on the resale market, so it really didn't put me out much. Your D80 is probably worth more than you want to mess around with, but you could always pick up a spare older body on eBay, depending on how serious you are about IR and how disposable your income is
