In reply to ogreville:
How cold did it get when you got cold? Not many people talk about 4 season bags anymore as its all a bit vague, but sort of decide how cold its likely to get and buy a bag that will take you down to those temps I guess. ME, Rab and others all have less expensive down ranges now plus you have Alpkit and other (Cumulus is it?) that do down bags that people really rate for value for money - so you might find you can get something for less that your budget.
Down is more expensive but with a bit of care (don't store it wet ever, don't store it compressed) a decent down bag will last decades. Synth bags loose warmth much quicker, or at least those I've tried have done and others report similar.