If you are willing to do a lot of work, you can find the sofa of your dreams on a budget. You just need to decide what you want, how much money you are willing to spend - and where to look.
Floor Samples - Periodically furniture stores sell their floor samples in order to make room for new stock. You can find designer styles for much less, but a few caution are in order. Typically, the sofas will no longer be under warranty. So check the construction carefully. Also check for stains, tears, and other defects that may be hidden. Make sure the sofa is the one you want because most are sold as-is.
Craig's List - There are many sofa choices available used on craig's list. Be sure to inspect the sofa before you buy. Don't take the seller's word about the condition. Check for stability, support, and stains.
Thrift Shops and Yard Sales - Inspect the sofa before you buy, Sit on it and check the support and stability. Check for smells as well. Dogs, cats, and smokers may have used the sofa before and though the seller may have used a couple of bottles of deodorizer before showing the sofa, a close sniff will reveal the sofa's true history.
Though I have given you a few sources for sofas, there are others - relatives or friends that are moving, neighborhoods holding a swap meet, or even reupholstering your old sofa. There is a sofa out there waiting for you. Now go out there and find it!