I would assume you have the factory 1.0 firmware, but I could be wrong. Just burn the ISO (only about 40MB) and pop it in...if you can update, it will ask if you want to and go for it.
If you've already got 1.5, then you've only wasted a CD-R and about 3 minutes of time.
And congrats! The XA2 is amazing. I definitely want to snag one of those eventually...probably after gen 3 comes out and they get below $400.