Inspired by the 8-bit guy's project I've been thinking about how to build a cheap 65c816 system and I've decided to do it as an emulation.
Hunting around for a PIC32MZ development board I found this.
https://www.mikroe.com/mini-32-for-pic32mzA 252MHz (415DMIP) 32-bit MCU with 1MB of flash, 512K of RAM a load of peripherals and a 32/64 bit FPU (time to put that coprocessor instruction to good use!). All on a 40 DIP carrier board for $29. The raw chip is only £7.42 and a hand solderable 64 TQFP if I wanted to use it directly.
I think I'll provide 384K of RAM to the emulator and 128K of (OS, Basic, Forth, etc.) ROM image with a small 4K boot ROM copied into bank 0 RAM at startup (00:f000-00-ffff).
For video I'm thinking of 800x600 SVGA monochrome (like an original Mac but better than 512x342). Driven from the PIC by DMA'd SPI it should use minimal CPU time. PS/2 mouse and keyboard inputs (you can still buy them!).
I'm not sure how fast i can get the emulator to run but I suspect over 8Mhz equivalent is possible.
At least two UARTs and an I2C bus via a slightly extended instruction set (via COP or WDM maybe).
As it will run at 3v3 interfacing to an ENC28J60 networking chip would be relatively easy.
For sound I was thinking of two SN76489 chips (3 stereo or 6 mono voices) but I'm not sure how to mix those.