If you want color, then the IIIc it is. I strongly recommend going to a store and looking at a IIIc before buying one. Several people I know, including myself, find the IIIc screen pixelated and hard to see. Others love the screen and the color applications that have started popping up to use on it. Every Palm unit has the ability to connect to the Internet.
Several modems are available for the III series and V series units.
Springboard modems are available for the Visor and a CF modem is available for the TRGPro. However, the Palm VII comes with built-in wireless connectivity. Unfortunately this connectivity is limited to email and web clipping technology best suited to getting short news articles, sports stored, directions, or information on the weather. Decide which group of features are important to you. If you are a heavy reader, I'd buy a TRGPro for its easy memory expansion.