Building on Joe's earlier comments, I think that the Mac Mini's video card is more than adequate for Accordance. I suspect that Raoul's previous issues were related to the quality of his Dell monitor compared to the cinema display of the iMac, rather than the Mini itself. If the clarity of the text is the top priority, then it's difficult to beat a cinema display. However, if cost is more important, you can certainly combine a Mini with a good third-party display and spend less than you would on an iMac.
I have a Mini in my office, and it runs Accordance swiftly and effectively. The text is not as sharp as my iPad or other devices, but that isn't because of the Mini; it's because the displays it's connected to are nowhere near the quality of a cinema display. (Perhaps someday I'll find room in the budget to upgrade them!)