Hi hk
I have an idea.... here goes

Setup the DIR-655 with WPA2-AES with a 63 character passphrase and match that with your notebook adapter.
Here is the scenario .....
Two wired PC's
01:xx:xx:xx:xx:xx (this one is used to access the DIR-655)
02:xx:xx:xx:xx:xx
One wireless PC (WPA2-AES w/matching passphrase)
03:xx:xx:xx:xx:xx
If you choose ALLOW Network Access, then input 01, 02 and 03.
If you plugin a third wired PC, it will NEVER get network access, because ONLY 01, 02 and 03 are allowed. Also you would never remove 01 or else you have locked yourself out of the router, unless you can use 02.
The drawbacks with this is that IF you plugin another wired PC, you MUST use 01/02 to ADD the MAC of the newly added PC. It now becomes a pain to remember that only three PC's are allowed to access the network. If you add a network printer or NAS to the router, you will need to add those MAC addresses.
The benifits are that no NONauthorized PC can get into your network. If some smartalec maintains that he can break your MAC address (not impossible), he will not be able to break your WPA2-AES. If you are fixing a virus laden PC, you can plug it in to the router, but it will not be able to infiltrate your network because its MAC is not allowed.
You are telling the "smartalec" that he will have to break two locked doors and to accomplish this he has to use software to figure the MAC address AND take 12-24 months to reverse engineer the encyrpted 63 character WPA2-AES passphrase.
If you do not add other wired PC's, then it will remain fairly static, however, if you add and remove a lot of PC's, then it becomes a royal pain in the fingers.
In your case, I would suggest that you could use the Z5, as that is acting as the DHCP server, to restrict the MAC addresses.
Cheers
