Snake Eyes,
I've no experience with 'Mac's so take this for what it's worth. I do have some experience with 'Windows' based stuff so will tell you a little about that aspect.
Most of the 'digital' modes can be done without a modem of any kind. Basically, all you need is a sound card in the computer, and a means of connecting that sound card to the output/input of a radio. Software 'modems' are fairly common, sort of.
The biggest problem is making the computer and radio 'compatible', getting rid of, or stopping any RF interference. Quite a few of those thingys on the market now, and not all that difficult to make if you feel like it.
Just to see if you might like PSK31, or several of the other modes, try finding the applicable software, install it, get an audio cable to connect the output of the radio to the input of the sound card (speaker on the radio, mic/aux/whatever input on the sound card). Listening is pretty easy. Transmitting doesn't have to be that easy, one or two 'gadgets' to put in line, sort of.
Biggest difference between the sofware programs is the user interface, the 'control panel' you look at on the screen. Some are 'nicer' than others, just depends on the individual. The basic programs all 'do' the same thing, basically.
Try it, you'll like it...
- 'Doc


Bunch not said in the above! Untill you find that you want to 'do' this stuff, why go to the bother? Sort of... Oh #3||, why not!