If you can get all 5 gears for $800 new from Subaru you're doing better than me.
I'd sugest you get 1st to 4th and re-use 5th to save a few bucks. Change any bearings that have any movement or gritty feel to them, get new synchros, a new input shaft seal and reassemble it with due care. (use the genuine Subaru manual, not a Haynes or Gregorys) Use 3 bond to seal the cases, and use gaskets for the back section (don't use silicone)
Brand new gears will last a decent time with respect.
I'm sceptical at anyone selling 'reconditioned' gearboxes for ~ $1200 - $1500, they are better described as 'repaired'. Depending on the seller you'll find very little (if any) new parts in them.