Nice work! What I'd give for skies that clear... mine are pretty good, but they sure ain't that good. Lovely capture of the small & large magellanics too.
I'll be interested to see what others say, but I kinda think you're at the limit of your camera there and there's not much to be done. To get more detail you'd need a) longer exposure times, b) higher ISO, or c) a faster lens.
Longer exposures will make the stars into lines instead of points, so not a great option.
Higher ISO will make the images really noisy, which no-one wants.
A faster lens and/or a new camera with low noise levels at high ISOs will produce the best results, but I expect it's probably not worth $3k+ to you!
Best suggestion would be getting a Star Adventurer:
http://www.bintel.com.au/Mounts---Tr...oductview.aspx
It's a little tracking mount that enables much longer exposures. They're a great, relatively cheap & easy way to get into long exposure night photography. Best for widefield shots but I've seen them used with zoom lenses to great effect too.