Sorry nobody has responded since now. Im not the APRS expert but I have set my system up.
If all you want to do is APRS you dont need an expensive TNC. Any old thing will do. Im using an old PK-232 tnc I got for $100. You might want to try using soundcard packet radio (http://www.qsl.net/soundcardpacket
). It basically turns your PC's sound card into a TNC. You should be able to setup 'receive' APRS capability without much effort or special cables. Simply plug the speaker/headphones output of your radio to the input of your soundcard and you should get the idea if you want to keep getting into APRS using the soundcard. (read up before you do this as there are some warnings about overdriving your soundcard and doing damage and what not)
I've tried APRS with 4 different radios from a mobile dual band to a hand held and they all work fine for APRS, assuming you have the right cables
If you are good with Linux you might want to consider buying a cheap TNC and installing Xastir (www.xastir.org
) as your APRS gui interface. It can igate to and from the Internet.
Internet bandwidth is of minimal concern unless you intend to be *THE* gateway in your area. As a new APRS sysop I would recommend that you simply 'use' APRS for a while until you get the hang of it. I've been playing with APRS for about 2 months now and I did look into being an igate and decided to adventure someplace else in the ham space