Bharti_Airtel_9800_126.96.36.1996 - Downloads - BlackBerryOS.com it is very stable and I'm getting 3G in my house when I never got anything better that EDGE with any other OS. I have not tried SKTelecom_9800_188.8.131.523 - Downloads - BlackBerryOS.com yet because I'm still very happy with v706.
DM tells you that 534 is up to date because your carrier says so. RIM says differently by releasing more versions.
If you decide to upgrade, do not use DM. Instead, go to All In One Guide - How To Upgrade Your Device - with Pictures & Videos. Read thru it a few times to become comfortable with the steps. Also, because you have an OS6 device, you will not have to wipe your phone clean and discussed in step 3.
If you have any questions, let us know.