Hi Gitpicker,
You've gotten some pretty good advice so far... BUT, I haven't heard anything about how you plan to charge your new AGMs. You definitely can charge AGMs with your run-of-the-mill converter, but you'll get much more out of them in terms of performance and service live if you give them a little bit of extra charging love.
IMO, the batteries Optima is producing today are junk... you couldn't pay me to use them. If you have your heart set on AGM batteries then spend a few extra dollars and get Lifelines or Odysseys (the Sears Diehard Platinum AGMs are identical in every way) and invest in a real charger as well.
If you don't have the budget to get quality AGMs (& charger) then I would suggest you stick with FLAs.
Hope this helps.
Cheers,
Mark