Iain M. Banks is one of my all-time favorite writers. I have to admit I'm not familiar with his non-SF output, but his Culture novels (and
Against a Dark Background, a standalone novel in a different setting) are first-rate space opera. I also like Peter F. Hamilton; I just started the second book in his Void trilogy, but you may want to start with the Commonwealth Saga (
Pandora's Star and
Judas Unchained) to get the background to the Void books.
If you like the Dresden Files, you may enjoy early Anita Blake, through
Obsidian Butterfly. Be warned, though: starting with
Narcissus in Chains, the series basically turns into endless vampire/werecreature BDSM porn, with a heaping dose of homoeroticism. Pity about Hamilton's
breakdown.