My '95 Legacy wagon hit 400,000 a few weeks ago (now a little over 402,000). At some point I'll need to replace it (AT has gotten pretty sketchy and I'm starting to smell fuel a lot), but I'm (irrationally?) scared of the 2.5 engines. Are there any newer models that approach the reliability/durability of these old Legacy's? How are the newer Imprezas with the 2.0 engine expected to hold up? At this point the thought of buying another 20 year old car isn't so appealing. I'd like to get something with more airbags and structural integrity. 

I used to have the same "aversion" to the 2.5s as you... then I got myself a nice little 2002 Forester with the EJ251 - not a bad car at all. In fact, I am quite happy with it.

the other half has a 2006 LL Bean Outback with the 3.0 and it is quite nice.

the one to really stay away from is the EJ25D (dual overhead cam version) - that one was loads of trouble.

Maintenance history (if at all possible to obtain) and/or carfax report can tell you a lot about a car. The report for my Forester noted that the head-gaskets had been replaced around 108K, & it had no accidents listed (the condition of the car bore this out). It also told me that I was only the 3rd owner of the car, with the older gent I got it from being the 2nd.

Careful looking can find you a nice, well kept car that has had good maintenance over its life. Don't be afraid of the 2.5, just be aware of the potential issues that could come up with one that has not been cared for properly - same as with ANY car.