I recommend the Honor Harrington novels for "plausible" Sci-Fi combat scenarios. Over the series of novels, the style of space combat changes dramatically multiple times as factions develop new technology, strategies, and tactics. They're quite a fun read.
Well the science was deliberately concocted to allow for the recreation of naval sail sea battles (ships that can only shoot "broadsides" because of the physics of the propulsion system, for example), but it was so well done that I didn't care (in fact is was rather fun).
You can buy the later hardcovers and get a CD with the entire series on it. I do recommend Baen for books because they sell at pocket book prices and have no DRM.
