If you are talking about ARM7 with LAN are you talking with operating system? If yes, are you talking RTOS or Linux?
If RTOS, you can use embedded Flash memory, smaller chips, much easier design, no external bus.
Most multimedia applications require lots of MBytes and so they do require an external bus. Although I really like the LPC2148, the max memory is 512 KBytes, for the Atmel SAM7X it is only half that and both would not be appropriate for high memory requirements. The Samsung device is very different, no embedded Flash, much more complex design of the PCB and software but it does support lots of memory. So, it might be the right choice, depending on what you really want to do.
Bob