If you have an ethernet jack near the fish tank or can run a wire from the fish tank (connected to the ACIIIPro) to your router or hub, then you don't need the Dlink - you can save about $100 there. All you need to do is somehow get an ethernet wire to the fish tank and you can do without the DLink. In my case, I couldn't run the wire so I had to go wireless.
The webserver on the ACIIIPro has fewer features than aquanotes. You could always try it and see if it is enough for you. It will not make the nice pretty graphs like aquanotes will, it will not send email alarms if your email requires authentication (it will do it if the email server does not require a password for outgoing email), You can't store notes etc. and once the log inside the ACIIIPro fills up it will overwrite the oldest entries. Aquanotes will constantly poll the ACIIIPro and download the log. For example I have over one year of log entries for temp, pH and ORP on aquanotes, every hour, every day, for over a year.
The ACIIIPro webserver will however allow you to view tank stats in real time, view the log stored in the ACIIIPro and view and make changes to the program running inside the ACIIIPro. This last feature is very nice since you can modify the program with a keyboard instead of punching buttons on the ACIIIPro front panel.
Some people have hooked the ACIIIPro up to their home network and have configured their router to direct web access to the ACIIIPro so that they can check the tank stats over the internet while away from home. All this can be done without a computer running aquanotes.
But for what its worth, I really like aquanotes since I can log in notes about water changes and livestock issues and capture data pver a long period.