The Amiga guide on the '2.54' disk lists the version up to 'Screech V2.25', so I'd say it's actually that and not 2.54.
No worries prowler
Next time just have a quick look in WinUAE
Edit : The 2.51 version is indeed AGA. You need to assign 'screech' to the folder on your HD in order to get it to work...