I recommend doing online research at Crutchfield because they guarantee fitment so you don't run into issues.
The 2005 Outback's head unit does not have any weird signal processing which means it will pretty much let a speaker's characteristics be revealed - that's a GOOD thing.
Make sure that the speaker is efficient if you're just replacing stock speakers. Crutchfield has a speaker comparison tool that either lets you compare speakers with equal power or equal volume. Choose the equal power comparison so that a speaker that is too soft will reveal that weakness. Louder isn't always better, but you can discern both clarity and volume at the same time. At normal listening level if two speakers are identical but one is louder, the louder one will sound better.
The 2005 Outback's head unit does not have any weird signal processing which means it will pretty much let a speaker's characteristics be revealed - that's a GOOD thing.
Make sure that the speaker is efficient if you're just replacing stock speakers. Crutchfield has a speaker comparison tool that either lets you compare speakers with equal power or equal volume. Choose the equal power comparison so that a speaker that is too soft will reveal that weakness. Louder isn't always better, but you can discern both clarity and volume at the same time. At normal listening level if two speakers are identical but one is louder, the louder one will sound better.