A. The problem is that your modems cannot send faster than 33.6k. The 56k technologies, such as X2, K56flex and the new standard V.90 are asymmetric - 56k from a service such as an ISP to you, and 33.6k (maximum negotiated rate, may be less) from you to an ISP.
Having one of your V.90 modems call the other won't create a connection faster than 33.6k since neither side can transmit faster than 33.6k. The 56Kb is possible because the line from your house to the telephone company switching office is analog, and that the rest of the path from the CO to the service (ISP) is 100% digital. At the service end, they specifically install digital modems designed to operate as the service end of V.90/X2/K56flex connection.
This means you would need on of the boxes the same kind of modem that an ISP would buy. You may find however that you can't get one of those without also having the digital phone circuit to connect it to.
If you need 56Kb look at ISDN. The easiest way to setup a system which can accept 56K V90 incoming connections is to get an ISDN2 or home highway and a 3COM Courier-I modem. The Courier-I can act as a standard and ISDN modem. It will also act in V90 mode as a server it it detects an incoming analogue call across the ISDN.