I just got a Kelty Light Year 20º and I like it a lot, though I've only used it a few nights so far. I think it's "comfort" rating is 32º, and it's comfortable for me at that temp.

But I only paid $132 with shipping. Mine is last years model and it has 600 fill-power down, the new one has 650 fill-power down and it's over $200 now.

I suggest you search around to see if can find one of last years for the same or less than the price as I paid. You're still within budget if you do, and you'll be good for a few more degrees of coldness.

http://www.campmor.com/outdoor/gear/Product___43167

I'm sure it's heavier that the one you're looking at, but the added weight is all down.

One thing I'll note is that I'm 5'9"/140bs and the bag fits me about perfect. I don't think it'd work well if your taller or weigh more, in that case you might want a larger bag.