As I don't have much experience with APS parts, I can't really comment on them.
As for the K&N though, I use it and think it's good from performance to fit and finish. It installs easily and is a very nice piece. I did notice that it does lean out your afr's (yeah I know, duh... that's how intakes make power), but with some minor fuel tuning, you should be golden. I still had to pull alot of fuel in my map (utec), so it's not like I was dangerously close to running lean.
Make sure that you get the one with the heatshield. If I were to choose between the Typhoon and another intake, it would be the SPT one.
On a side note, since you've got an STi, I'd tell you to get it. With some tuning and some good boost, you'll really appreciate the extra flow. Another nice addition to your set-up would be a better IC. This is just my opinion though. I checked out my buddies STi, and with minimal mods (I'm talking K&N, tbe, AP/ST w/protune, Prodrive bcs, and ebay tmic) just hauls ass.
Last run at the strip yielded him a 12.7 @ 110. That was without launching hard. Not too bad IMO.
My car is well, it's like 10 lbs of shit in a 5 lb bag...
<------ Click to see what I'm workin' with. ;)