I'd vote for stay with current setup, but that wouldn't be Xtreme
Imho it's worth upgrading when bigger performance gains are seen. So it's (4.), if that meant next gen of fermi, which i doubt to see sooner then another year to wait, or dual 5970. (2. less power usage) & (3. psysix support) won't be that much of performance gain from current setup to justify purchase(including new fc waterblocks)/upgrade .. and just for dx11 support it's not worth it imho ..