I have V7 STI Wagon takeoffs + SPT springs + group N mounts. The left rear is shot. I am having great difficulty in finding affordable (less than $500) struts that fit the wagon. I have Koni inserts on my '05 Legacy GT which I like a lot but they are like $700 and you still have to cut up the strut. Only direct fitment I find is KYB GR-2, which are probably not up to the task of controlling the SPT springs. What are other members running?
Do the koni's. The install isn't that hard and they are great dampers. The only direct fitment is the KYB's that you found (maybe some KYB AGX's, but they aren;t much different), and no they will not have enough damping for your springs D-specs are great dampers, so I've heard, but they will give you camber issues on your wagon. Some people don't mind this, but others have ended up with severe positive camber that they could not adjust back to a safe range.
If you just need something to hold you over I would find a set of stockers. Continue to save for a setup like the D-Specs.
I found KYB AGX for the wagon for 445 here http://www.cvrmotorsports.com/store/index.php?target=products&product_id=212
Only issue with those, if you look at the part numbers, is that the front is for the older RSs and the rears are for bugeye WRX sedans. Its the classic mismatch that kinda works but still has some camber issues. Yerrow, what are you using to control your alignment? Camber plates, bolts, adjustable lateral links?