As far as I know, the 80mm 5.6 are good lenses... I own a nikkor 80 5.6, but so far have only printed 7x7's with it. It's definately sharp in those enlargement ratios.
BTW, I use it at f 11, 2 stops down from wide open.

On the other hand, a professor once told me to use a 80/4 componon-s at 11 as well, just as I should the 50/2.8 at f/8, not 5.6

As an irrelevant piece of extremely biased info: I like my 80 nikkor better than the 80 componon-s I used in college. Mostly because the nikkor is mine.

If I recall correctly, I paid less than 50 for it on ebay, and it came with the adaptor for leica 39mm thread and a locking nut.