The PC guts seem boring and will inflate the price. Why not do a reissue with functionality closer to that of the original, based on the C64 DTV [1] which cost $20 or $25 when it was on the market, and sell it at a $50-to-$100 price point?
Anyone who is interested in this stuff that hasn't heard Jeri Ellsworth's Google Lecture about her life and her experience designing the C64 DTV 30-games-in-one joystick must watch this.
And if you aren't sufficiently impressed by that, look up her from-scratch pinball machine or her basement CMOS fab or any of a million other things. I am in awe of Jeri's creativity and her ability to find the time to do so much cool stuff.
[1] http://en.wikipedia.org/wiki/C64_Direct-to-TV