I always keep the vsync setting in 'always on' mode. If you're displaycard limited the FSAA settings are the first place to start cutting from. 2XAA won't do much difference except slow down the performance.
You shouldn't care about the top refresh rate (except that one should always keep it at 85hz minimum to avoid eye wear). Setting it higher or lower won't affect your gameplay, with vsync on you should keep an eye on the _minimum_ framerate not maximum.
If your frames aren't dropping even at fully burning fields and multiple enemies around, you're as well equipped as possible.