That 30" display was a beaut, but I figured out a while ago I like multiple monitors rather than huge ones. I have the 21.5" iMac with two external monitors flanking it. My 20" Dell monitor started leaking magic smoke, so I replaced it with a 19" Samsung. You can get amazing deals on smaller LCD monitors at thrift shops these days.
There's a company called DisplayLink that makes USB video adapter chips. A lot of companies use their chipset, which has Mac and Windows drivers. They usually run about 50 bucks, and while I wouldn't want to use one of those screens for gaming, they're great for browser windows and Photoshop palettes. I'm thinking about adding a fourth screen next time I see one of those adapters on sale.
Thank you.