Thanks for the response! Yeah, I've looked at most of those options. I'm not thrilled with any of them.
The FV-1 has a lot of traction, but I dislike the closed source, Windows-only toolkit and assembly programming. I don't see it as an upgrade from the ToneCore for prototyping.
I'm considering an ARM Cortex-M based solution (Teensy 3.x + BlackAddr guitar adapter). The adapter is well thought out and I'm much happier with a GCC based toolchain. The 16-bit Teensy audio library isn't ideal but if I toss that it's a reasonable 24-bit piece of hardware. My concern here is mainly CPU cycles -- will it keep up for high end effects?
I haven't looked into the OWL much. I want something that doesn't cost $300 to replicate if I want to give a friend an effect.
There's a guy on the DIY stompbox forum that is putting out boards based on the XMOS multicore processor line. This is definitely interesting but kind of a mixed bag. The toolchain is closed source but they have OSX and linux versions available. They can be programmed in C but it's a weird multiprocessor C variant. My real hangup here is the viability of the XMOS line. It's pretty new and not widely adopted. I know ARM boards will be around in 10 years, will this?
I'll probably keep struggling with the ToneCore for a little bit since I've got the hardware all working. I'm really struggling with simple arithmetic for some reason, even though in the past I developed a fairly complex effect on it. Once you get something working they're nice pedals, and I have a couple docks, might as well do something with them.