Are you talking about summer or winter?
If summer, my opinion is to go with a fleece bag liner or an Army poncho liner. I live in Alabama, so I know the heat and humidity. Unless you're just terribly cold natured (and if you're cold in this heat, go to the doctor!), even a warm weather bag is too much from April through the middle of October.
If you're talking about winter, I don't have a good answer for you. My current bag (a TNF Cat's Meow 15 degree) was free from a friend, and the other one was $5 on clearance at Walmart.
From what I've experienced and have seen around here, though, a sleeping bag is one of those things where you get what you pay for -- in other words, save your money and buy a good one. Watch REI for their sales. Maybe you can use that Amazon card on something else, freeing your cash to go toward a bag.
"Stand in the ways and see, and ask for the old paths, where the good way is, and walk in it; then you will find rest for your souls."