supposedly Subaru gets the 'best' re-man'd axles from cardone - so I've read anyway.
it's a fair gamble, I'd hope that it will be OK but, many people report problems with remanufactured axles; leaking boots or vibration. Likely many folks have used them and just don't get on the internet to report satisfaction. but they WILL complain if it's bad!
But a Subaru axle that hasn't been exposed to too much grit, road salt or water thru its split boot, can be cleaned, re-lubed and re-booted and will almost always be better than an axle that has lost its case hardened surface by grinding/machining and had cheap oversized ball-bearings thrown in it.
I think starting in 05 or 06, Subaru went away from the axle stubs held in with roll pins so, as cardoc mentioned, if you keep looking your 04 should have a roll pin. Search for axle installation info. Very common repair.