I'm a fan of high-quality down bags or quilts. I really like the Jacks R Better quilts and Western Mountaineering bags. Save your money and get a good one or two and they will last you a very long time. I bought a WM MegaLite bag on eBay for 1/3 off and sold it on eBay two years later after ~30 nights' careful use, still in great shape, for more than I paid for it.