400+ is generally good. I say generally because the thread count can be misleading. With 2 ply sheets, it could be 2 - 300 fabric put together and sold as 600. The best way is to go by touching the samples. If you're buying online, try to find out the weave. Close weaves feel more like silk, twill is more like the flannel, and plain weave is probably what you might already be use to. Also what kind of cotton used is a factor. People rave about Egyptian cotton.
Hi J! Check out Bed, Bath And Beyond for reasonable price good quality. You will have to hand over the $$ but it will be so worth it.Wait and save up if you have to, it's a luxury worth waiting for. ( QVC actually has decent bedding as well)