Changing the belt? Maybe check the pulleys too. (The bearings might getting worn).
The 4R doesn't have the famous "problems" of the Subaru H6 engine in my other car (Subaru Tribeca 2006). But, if you're looking at a belt change from "funny noises" or long term wear-and-tear, it might be good to give the idler puller and tensioner pulley a spin while the belt is off.
They should be smooth and almost noiseless. If they're not - look into replacing the entire pulley ($25-35), or maybe just pressing and replacing the bearing in the ones you have. (Costs only $3 per bearing, but it's a slightly more skillful job.)
For a "noisy" or wiggling tensioner, you may replace either the complete assembly (moderately higher $$, more work); or just the pulley assembly (medium $, less work), or just the bearing (least $, more work).
You don't have to do the bearings and the belt at the same time - remove the belt, check the bearings, put on the new belt, and letter take it back off for bearing and pulley replacement.