The Prelude is a lower-to-midrange arranger, the usual price in Euro is about 800-900 €. I think it was released around 2009. It is identical to the GW8-E, it just has on-board speakers in addition. GW8 and Prelude have the same sounds as the SonicCell, most of them are rather identical to the Fantom X, (some are a little compressed). There is an additional section of world sounds in the Prelude and GW8-E. I think the quality and quantity of sounds is quite ok and definitely better than you would expect regarding the price.
However, if I had to choose between Prelude, GW8-E and GW8-L, I would definitely take GW8-L (Latin), as its world section has a lot of sounds from the high-quality SRX library.