I have been using Opera in most of my builds as it runs a lot better than Firefox on these. Dont know if Opera suits your needs or not however if its a deal breaker I may be working on something with iceweasel in the near future.
As for networking the network manager wicd can be scripted to access the same network without prompting. The good result is that it automatically signs on for you even in encryption is used. The bad part is that if you switch air cards or dont put the air card in the system runs hot as it will be looking for the card. Other than that wicd will suit your needs on WAF.
You have not provided enough information on your wireless card for me to be able to tell you if any of the builds I have made will work. Most all of them have madwifi in them. Madwifi supports many atheros based wifi cards. Here is a small listing of 3com products that madwifi supports.
http://wiki.lapis-linux.org/index.php/Hardware_Supported_by_MadWifi
Looks like the 175 in a couple of models is supported.
Audio is not trivial on these as the media players take up some real estate. Slackware 12.2 has good integration of a media player in it and it also has wicd. Opera is installed but you can easily install firefox with this command as root:
Debian LXDE would be a second choice. Once can use apt to remove and install on debian.
There are some front ends in linux for different things. May I ask what you needed .net for?