Chris,
The DX7 is indeed a great piece of synth history. Keep in mind that if acoustic piano is an important part of your arsenal, you ain't gonna get it with a DX7, or any of its close relatives. A contemporary $300.00 arranger keyboard such as the Yamaha PSR292 will have a much better piano sounds and a lot of other very usable sounds, many of which will blow away anything you'll find on the DX7.
Midnite