I'm not sure what the most recent update for your region is but if you download and install Kies to your PC then it will tell you, alternatively you can look for an app on the Android Market called Check Fus
Market link here
Check Fus is an Android application which will check your device for the latest update in your region.
Your other option if your interested would be to use Odin to flash your SGS2, firmware packages including Frankenstein packages are available on Intratech's thread over on XDA Developers Forum
. You'll also find a link to download Odin and a guide to flashing your SGS2.