Hi Ronaldo,
When the SFE/SGE series products went to version 3 of the firmware we saw much better support for VLAN and other features such as IPv6. That might account as to why admin guides were missing content on IPv6 as they may have been references for Version1 firmware and not version 3 firmware.
All SFE/SGE's now support version 3 code.
If you do not need the stacking support from the SGE/SFE series why not look seriously at the lower cost SG300 and SF300 series.
Very good IPv6 functionality built in these units, see following URL on the new SG300/SF300 series. (this family is really a refresh of Silicon/Operating system and packaging of the older SRW series. http://www.cisco.com/en/US/products/ps10898/prod_models_comparison.html
Also if there is a failure of the new SG300/SF300 series switch, the support center will forward replace the unit for next business day delivery, where applicable.
hope this is of use,
regards Dave