We already have WinUAE that can perform like a 2Ghz Amiga. So...
I would want to see something better than that (more features etc.)
Not to fussy about the price, but keep it under $1000 or I would never buy it.
For running modern software I think dual core 1Ghz cpu is the minimum.
You might want to find out what type of software people want to run on it. What kind of spec do you need to play HD movies? I might like internet radio, not so much HD movies.
It's very interesting, if you finish your final spec soon, I will actually believe you can do it.