Passage at Arms and The Dragon Never Sleeps by Glen Cook. Weber and White wrote the Starfire books Insurrection, Crusade, In Death Ground and The Shiva Option. The fleet combat will be really familiar to you. Walter Jon Williams's Dread Empire's Fall Series: The Praxis, The Sundering, and Conventions of War.
Then there are other authors/series that are more focused on small unit action, space marine stuff, but with some space ship battles included as well. John Ringo's Looking Glass series: Into the Looking Class, Vorpal Blade, Manxome Foe, Claws that Catch. First book is classic aliens invade Earth stuff with a scientist & soldier protagonist-pair, then the second book takes a turn towards Star Trek-style space exploration. Then there's the three series - Heritage Trilogy, Inheritance Trilogy and the Legacy Trilogy - by Ian Douglas (aka William Keith). It starts with various Earth powers fighting among themselves until aliens show up and the fighting moves to the stars. Lot of small-unit infantry action, with protagonists changing as the years (and later decades) pass. It starts with little silly, with US at war with French-led United Nations but gets better as it goes along.
For harder sci-fi, try Peter F Hamilton. Both the Night's Dawn trilogy and the two-parter Pandora's Star & Judas Unchained. Lot of cool concepts, lot of characters, lot of action. Be warned that these are HUGE books, it'll take a while to read them. I haven't read the sequels, Void Trilogy, but it has received praise too.
