I just got Finale 2007 and have been exporting my scores as .mid and then importing the .mid into Sonar, and assigning the separate tracks to the Miroslav Philharmonik orchestral plugin. The results are SO much better than GPO.
EWQL comes in many flavors and also sounds fantastic, but to get the best results you'd probably want to the GOLD XP edition which is about $800, or twice the cost as Miroslav. (it probably sounds better than Miroslav in some areas, but for $400 Miroslav will give you plenty of great options)