The Tech Report - Improving the PC as a gaming platform: the hardware.
The new spec would clearly involve some compromises, since you can't simply step up and demand that every new computer feature a Radeon 7970, 32GB of RAM, and a six-core CPU with Hyperthingamabobs. However, let's take a page from our own System Guide's Econobox. MPC-HD could set the bar at, say, a Radeon 7770 graphics card ($120 or so) and a Core i3-3220 processor (around $130). Those components provide solid gaming performance at 1080p in the vast majority of titles, even with anti-aliasing enabled. They would be a perfectly reasonable baseline to aim for—one that provides many times the horsepower of current-generations consoles.
Setting a baseline would make life easier for developers, as well. Let's imagine MPC-HD has multiple levels, and when publishing your game, you can simply state that the minimum requirement is MPC-HD Level 1. That's easy for developers to code for, easy for buyers to follow, and easy for manufacturers to advertise and profit from. One can only wish.