I'm pretty happy with some refurbed Polycom IP501 phones we picked up recently (so much so that I've dumped the newer 450 I started with).
They are in the $100-$150 range on fleabay, and very easy to get running with the Endpoint Manager add-on (but virtually impossible without it).
Three lines, good sound quality, excellent build, and the speakerphone is very good. They don't do POE, if that is a concern.
Its night and day compared to the Grand Stream 2000, that phone will be sold or tossed on the spare heap.