Here's another thought: have you bought a tent yet? If not, what is your budget?

For $90, you can get an REI Minimalist bivy sack (and $20 - $30 for a small coated nylon tarp, in case of rain) instead of a tent. The bivy sack will also add some warmth to your sleeping bag. And, your total shelter/sleeping bag system (with the down bag I mentioned earlier) will cost $200.

You'll end up with a versatile, flexible, inexpensive system. Good luck.