From the names you have mentioned they all all going to be attention grabbing (noisy) items, the AutoExe boxed intake is pretty loud, probably not far off any other SRI Ive heard, as are most of the mufflers listed (especially the Corksport).
Intake,
A quieter intake option would be the BEGI airbox, its still an SRI by nature, but its all fitted within a pretty hefty aluminum airbox, so it is quite muffled, you can still hear the turbo noises externally, just not as loud as other options. The quietest performance option would be a drop in K&N filter into your stock airbox, anything else on the market will give you an earful of turbo whistle and whoosh.
Exhaust,
I dont know that I have really heard of any quiet jap built exhaust systems, a good choice would be as Doc mentioned, a 3" magnaflow cat-back from Best mufflers, you wont see much in performance without also doing a downpipe, in fact you will get better performance from changing the down-pipe and retaining the stock cat back, than the other way around.
Springs,
I dont know the stock spring rates off hand, I have the Eibach's in mine and it is slightly lower (~15mm) and a tad firmer, not teeth rattling stiff like some of the jap coilovers.
Another item that helps these cars no end is a set of Cobb swaybars, these reduce the factory body roll, while still maintaining a comfortable ride.
I have heard a lot of good reports running Bilstein shocks, these are on my to do list.
I wouldnt knock the US gear too hastily, most of the parts for this platform have been developed and manufactured in the US, I appreciate that you may have had bad experiences on another platform, but I can tell you that the reputable US manufacturers are making some top notch parts for these cars, by comparison (and everyone knows how much of a fussy bugger I am with quality of after-market parts) my car is fitted out predominately with cp-e parts, the only jap branded part is my HKS bov, which was part of the cp-e kit.
From what I can gather about AutoExe, is that your paying premium dollar for sticker bragging rights, the parts are no better than anything else out there, if you believe that paying nearly double for a part that is just as good (or sometimes not as good) as its US counterpart, knock your self out, at the end of the day its your coin.
I dont mean to discourage you, but after playing with cars as long as I have, I really dont rate the majority of the jap "performance" brands out there, most of them are just highly polished crap that looks pretty under your bonnet.
Nearly all men can stand adversity. But if you want to test a man's character - give him power.
Abraham Lincoln