With this modem you are selling:
1. In terminal type AT+MS=?.
What is the tx(max)& the rx(max). 56000,56000 or 33600,56000?

2. I want to use this to also receive call waiting messages.
Your description "while this is a "voice" modem that supports TAM (telephone answering machine) functions, the quality of voice, and ease of use may vary! (I don't think it's worth fooling with: if you want a modem for telephony, this isn't the best choice.)"
What is the difference between TAM & voice?
Does this mean I can't hear a simple message?(I do have a sound card).
What do you mean by quality? (I'm easy to please if this just 'works')

3. What is the difference?
"If you haven't already come to the conclusion that controllerless and soft modems are better than "real" hardware-controller modems, it's time to re-think."
Is there a way to'look' at the card & determine this?

2. 'Call waiting messages' - Type 2 caller id comes with call waiting and is supported - this is when you are online(data) with the modem; your options are to ignore the call, or take the call - no 'voice' functions of the modem are used for MoH. 'Voice' functions are to use the modem as a TAM (telephone answering machine) when the modem is not online. Caller id for offline calls (type 1) isn't supported. 'Quality' refers to the audio quality/sound level of voice messages in TAM mode.

3. I don't understand the question.

The problem is: more often than not, the chipset used in any particular modem is not disclosed by the seller, distributors, or manufacturers.

http://www.agere.com/support/client/modem_dsp.html