Honestly, all of the big name standard SRIs (CP-e (http://cp-e.com/webstore/product/maz...no-air-intake/), Corksport (http://www.corksport.com/corksport-p...daspeed-3.html), 2XS (website in dev, but you can always PM him here)) should be close enough to be fine, particularly if you plan to get a tune down the track. I ran the corksport stage 2 with airbox for over a year without a tune. LTFT were always a bit off and would do some funny things on long drives, but nothing serious. Got an AP and now fine.
IMO: The only reason to be really pedantic about maf size is if you plan to never get a tune. If you do, then get one you like, run it for a while, save up, get an AP, and Bob's your fathers brother!
Note: Cobb (http://www.cobbtuning.com/MAZDASPEED...t-p/771500.htm) says theirs needs tuning, but this might just be a plug for their AP.
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Fast: RayD Tune|COBB AP|JBR|Stratified|CP-e|Xforce|Autotech|Denso|Corksport
Turn: Bilstein|Eibach|Whiteline|JBR|Hankook RS3
Stop: Wilwood 4pots|Custom lines|DBA T3|Remsa|TRW 600
Rice: JL|Alpine|Focal|MiniDSP|Rota g-force|2XS|Cree|Celestial Blue FTW!