You're in a fix. The best displays are still good old CRTs. If you were only working in SD, I'd say go that route. But, the buying sheep (er, I mean public) have decided they want the highly inferior flat screen LCDs, so no one's really making affordable HD CRTs anymore.
So you're either stuck with an inferior HD/SD picture, or you buy two displays, an inferior one for HD (LCD) and a better one for SD (CRT).