I suggest that "best" be changed to "projected". For development and prototyping, many systems are designed and simulated on machines with a small number of processors. With cloud computing here and swarm computing not so far away (and possibly quantum computing being realized once the physicists solve the hard problems), your best model of today and of yesteryear may soon be superceded by an adequate model of tomorrow. Even just understanding massively parallel processing well is a worthy goal and likely to be applicable to the upcoming shifts in technology.
Gerhard "Ask Me About System Design" Paseman, 2010.11.04