So here's what I'm looking for: an ultra-light summer bag that won't break the bank (under $200?)

I realize that LIGHT, WARM, and INEXPENSIVE do not all go together. Knowing this, I choose to prioritize light and inexpensive and am willing to sacrifice warmth because I sleep warm, don't mind wearing layers to bed, and I already have a heavier warm bag I can resort to if the temps really drop.

I'll be spending about 80 nights in the backcountry of the Eastern Cascades this summer (Pasayten Wilderness and Washington Pass area, primarily).
This is a fairly mild area, but when it does rain, I won't be staying home. The temps might duck in to the 30's, but 40's is most typical in the summer.

I'll be alternating between a hammock and bivy sack, using a tarp-shelter if I expect rain.

Some options I've been considering so far:

Vaude Sioux UL 100 - 19oz, 55 degrees (tough to find)
Lafuma Extreme 600 - 20oz, 45 degrees (tough to find)
MHW Ultralamina 45 - 20oz, 43 degrees (a bit more expensive)
Jacks R Better Sierra Stealth - 17oz, 40 degrees (a bit more expensive)

What other suggestions do you folks have? Thanks!