my sales are consistent and growing(except for 2/08) and I would like to increase traffic. I currently get ~3000 unique visitors per month. I just moved to a new faster server and would try for 6000+ uniques per month.
My advice is not to watch the toolbar PR - it's the wrong metric to be concerned with, and it is not always accurate anyway. Instead, be so good at whatever you do that you attract more backlinks naturally.
Also watch your server logs to see what existing traffic you can do a better job with. You may find ideas for what your existing traffic is looking for that you could provide -- plus more expanded language you can use and articles your can write in those areas that might get you ranked on a wider variety of searches.