I am going to only build 10 of the IOBoards. They are double-sided SMT, so they have to be hand assembled on one side.. real pain. I already have SDRAM boards and RTC boards (with MCP79410) that are built. I just have to add them to the website.
The MCP79410 is something that I have used in the past, and offers EEPROM and RAM on top of the normal RTC functions. I don't know if any core will take advantage of those, but they are there.
The MiSTer is nice because the DE-10 is inexpensive. However, the hardware difference (quality and features) of the DE-10 vs. the Replay (and new Replay2) is quite substantial. The Replay has a DVI connector, so you can output in DVI, VGA, or HDMI all from the same connector by just changing the cable... no add-on board required. There is 64MB of SDRAM (>200MHz), single SD card, expansion IO, dual DB9 joystick ports, 96bit audio, and composite/SVideo outputs. The daugher-board has Ethernet, another 64MB of SDRAM, multiple USB type A and Mini-B ports, 34 pin floppy drive interface, and a 68060 socket. Considering that a lot of the arcade cores for MiST/er have come from MikeJ (creator of Replay), you know the person behind this product knows what he is doing. I have been helping Mike with the Amiga stuff for several years, and I am the North American distributor for Replay.
I am the flux ninja