If you do the install yourself and pick a nice junkyard Suby (preferably in a running Subaru) you can save a few bucks over a CB Perf 2110. But not by all that much. The reason to do it is the reliability and maintenance breaks you'll get once it's sorted.
The EJ25 is a pretty good engine but a lot of folks here prefer the 2-cam version to the 4-cam. Setting up the timing belt in the 4 cam is a bit tricky, and these engines all tend to have weak head gaskets; last word I heard was that the 2-cam ones were a bit less likely to blow antifreeze.
Best is to get the engine, pull the pan and check the innards. These cases are usually very nice inside. Install the Small Car oil pan, replace the oil-air separator if needed, and do the oil pump if the car has more than 100k on it.
Then replace the water pump—use a Subaru part, not an aftermarket one. Pull the heads and have them hot-tanked and checked, and maybe decked. If the engine is young and wasn't beat on (which most NA cars weren't) you won't need a valve job.
Reinstall with new head gaskets and new head bolts. The old ones are fine—they look fine and work fine; they're totally reusable—but the book says spend $85 on new Subaru bolts and so do it anyway. Wait til you get a load of the head torque spec!
You may want to turn the water inlet backwards to point the business end at the front of the car, where your radiator will be. I didn't do it but probably should have.
You'll also get a new thermostat, also at great expense, from the Subaru dealer and not from NAPA.
With all those things done you'll be ready to rock on for another 200,000 miles.
If you get any flavor of Subaru engine you will have no need at all for a Berg 5 Speed. Those boxes are for high-strung Type 1 engines with peaky torque curves.* Your stock (or Franken'd) EJ2x has an anvil-shaped torque curve, like a High Plains mesa in the middle distance. Sacred Ground.
*(or high-strung drivers with cheeky attitudes).
