Cowon D2 is for abt 9k for 4gb version. while the creative zen is 8k for the 8gb version.
i myself got a creative zen 8gb just a few days back and m quite happy with it. the SQ is very good, compared to Ipod Shuffle and Ipod 3G, both of which i have heard with the same earphones (Crossroads Mylarone SVi).
Creative Zen 4gb:
Pros: 2.5" screen, expandable memory, rich video performance
cons: expandable memory almost useless as library doesn't integrate with internal memory. also some functions not available for files which are on expandable memory.
Cowon D2:
Pros: 2.5" screen, expandable memory, files on mem card integrate in the library, good video performance, best sound quality in the market (atleast better than the others mentioned here).
Cons: EXPENSIVE!!!!
havent heard D2 though, that is just after reading reviews.
may i suggest u one more player....
Sansa fuze 4gb:
pros: files on memory card integrate with the library, good sound quality, future firmware upgrades possible to add more functionality (just 2 weeks back, the new firmware enabled the fuze to play FLAC and Ogg files)
cons: small 1.9" screen, average video performance.
havent heard this one too, but people like the sound quality on this one.
and im not even gonna start talking abt ep630, way too many fans over here, just head over to headfi.org and ask people there abt the ep630 and they will give u the answers.