more variety *help me!*

[JesA]

well, i was looking at my Jpop collection, and i noticed that alli have is Ayu,BoA,Do As Infinity, and Namie Amuro. i really need a bigger variety of music and artists. so i got on yesasia last night, and started browsing thru all of my possible choices...i got an album from a bunch of different artists. but theres 20 dollars that i have left, and i need help deciding on another album. im trying to cover different styles. here's what i have so far...

1.GLOBE - GLOBE Decade Singles History 1994-2004 3 discs
2.hitomi - NEW ALBUM CD+DVD Limited Edition
3.Sifow - NEW ALBUM CD+DVD First press edition
4.Nanase Aikawa - ID2
5.Utada Hikaru - Singles Collection
6. ???

can someone help me decide what to get for the sixth item in the list? theres so much to get, but just so little money. is there anything yu would recommend me getting? (thats 20 dollars or under)