Regarding BitCoin, at this point you won't be able to find anything "better" than ASICs, that sort of defines the maximum refinement.
From a systems architecture perspective it is interesting to compare this to the Intel Larrabee project (lots of parallel cores) but that seems to me to have suffered a similar coding challenge that the Cell architecture has.
[1] http://en.wikipedia.org/wiki/Larrabee_(microarchitecture)