AFAIK, the XT530/531 are not very closely related to the XT3xx line. They mostly just seem to share cosmetic similarities with a different hardware platform.
Ignore what I just said, upon further inspection they do appear to be related, just based on the newer/faster msm7227T SOC.
Looks like I've got another device to add to my list.
Sent like a Streak of Light from Spidey, my Dell Streak 5
Sony Xperia ION "The PDA" (Quad-Band UMTS, 1.5Ghz Qualcomm 8260, Stock Jelly Bean) - my main brain
Alcatel OT-909s "The Phone" (Dual Band UMTS, 600Mhz Qualcomm 7227, Stock Gingerbread) - down for repairs
Alcatel OT-981a "The Backup" (Dual Band UMTS, 600Mhz Qualcomm 7227, Idontknow186's Gingerbread ROM) - my main phone
Motorola Spice XT300 "The Project" (Dual Band UMTS 528Mhz Qualcomm 7225, Modded stock Eclair) - WIP