In reply to wiggi:
I have a Montane Prism 2.0, which isn't down, but it's cheap, light and warm. Also it's warm when wet. Which isn't the case with down.
You'll find that a lot of the time you're actually very warm. I find that I can get away with a baselayer and a softshell in the Alps. So if you do get a down jacket, make sure it's a light one.
Rab sell a lightweight alpine down jacket:
http://rab.uk.com/products/mens-clothing/down/microlight-jacket.html
Patagonia also sell a 'down sweater'
http://www.patagonia.com/us/product/mens-down-sweater-jacket?p=84673-0-984
However I'd strongly advise that you get a good softshell. If you don't have one then ArcTeryx sell a really good climbing shell. Very expensive, but highly rated. This would be the best thing really:
http://www.arcteryx.com/product.aspx?language=EN&gender=mens&catego...