damn rex, you got a WRX and an MSP... get an HKS SSQV. its the best i know. if you wanna be VERY loud get an XS Turbo RFL (i think we all know what that stands for). as for the place to buy, try www.gruppe-s.com (i'm sure you know about them) or www.spool-turbo.com. just do a search on ebay for some blowoffs. word of caution tho. the XS Turbo BOVs are somewhat problematic. you gotta do it exactly right. as for the intake, SpicyMSP got the Injen contract for the prototype intake (as you know from the search). i don't know when its gonna be released, but don't ask Spicy. i don't know anything about the adaptors tho, sorry.
WOW Options for BOV:
Greddy Type S
Greddy Type R
1st Gen DSM
HKS SSBV
HKS Racing type 2 (wont be able to run unless mondo boost) (like above 18 psi i think)
Apexi Twin Chamber
Blitz Dual Drive
Flyin Miata
Turbo XS
ect
Adapter pipe yes:
HKS uses it own circle flange with a clip (b**** to install!!) (can get in dsm bolt up)
Greddy can be univ. or DSM flange
Apexi is the same I think
Blitz is a Universal
other I have no clue