I'm presently writing a little tutorial on PIC serial port networks, but until I get that done, consider a few things:

The best architecture will depend a lot on how many bytes you need to transfer, and how much latency you can tolerate.

If you use one or more 8723's as I suggested, you have a lot of options.

Each one (of the "slave" devices) can receive data from both ports on interrupts and store them in big buffers.

From there, you can -

1. Use the PSP port (PORTE) and transfer the bytes in byte-wide chunks between devices. You can use interrupts if you like.
2. Use a serial protocol like SPI. That is fast, and addressable. - and can use interrupts. 8723s have two SPI ports.
3. Use good old SERIN2/SEROUT2. Not particularly fast, and no interrupts, but because of the large buffers in the slaves, the master can ask for the data whenever it is ready.
4. Use SERIN2/SEROUT2 + interrupts. You can connect one or two extra lines from the slaves to PORTB of the master. When a slave wants to send data to the master, it pulls the interrupt line low. The INT lines are edge-triggered, so the slave only needs to pull the line low for a couple clocks and then lets it go high again (should be driven open-collector with a pull up). The ISR in the master pulls the interrupt line low from that end. When the slave sees the low, it transmits data to the waiting master.
5. Use the I2C slave routine I posted a few weeks ago. It is interrupt-driven and can transfer a byte in about 150uSec using (bit-banged) I2CWRITE on the sending end. 8723s have two I2C ports. The good thing about I2C is that it uses hardware addressing - it doesn't interrupt the processor unless there is an address match.
6. Roll your own.