I am not affiliated with either of the companies, and I am not advocating one system over the other, but here are my two cents:
The iA supercharger (non-intercooled) is supposed to increase rwhp from 150 to 230. That is an increase of 53% (not 38% as claimed on iA's web site). That's a very large increase. The following estimate of supercharged hp can be used (e.g., see Corky Bell's book):
HP_super = HP_na *
PR * DR * VER * DPE.
PR is the pressure ratio, DR is the air density ratio (boosted/na), VER is the ratio of volumetric efficiciencies, and DPE is the drive power efficiency (100% if belt is transmitting power perfectly).
For illustration purposes let's use DR=0.85 (ballpark for a non-intercooled system), VER=1.1 (better VE after supercharger install), DPE=1 (perfect power transmission). You can plug in other values and see what you get, but the values I used are a good starting point, IMHO.
Then, you can find that in order to go from 150 to 230 hp, you need a
PR of 1.64 (someone please check my math). That corresponds to roughly 9.5 psi of boost (again, please check). Why is this important? The Boxster is a fairly high compression ratio engine. That means you want to have low boost levels. 9.5psi to me seems too high to safely use on a Boxster engine with stock internals. YMMV.
Based on what turbowerx say on their website, their kit provides 6psi of boost, intercooled. They only claim an hp gain of 60 hp (to 210 hp). Plug in their numbers into my equation above, and you will find that this makes a lot more sense (
PR=1.4, DR=0.9 due to intercooler, VE=1.1, DPE=1):
HP_super = 150 * 1.4 * 0.9 * 1.1 *1 = 209.
(The last term is approximative, as there is no belt efficiency in a turbo system)
Of course, this is just physics, so real world results may vary
Bottom line: I don't see how iA can get 80 hp out of a non-intercooled supercharger kit at safe boost levels. Judging from the numbers on paper, turbowerx seems to offer more realistic power gains. Ask for dyno charts including A/F ratio and boost levels before buying.
Gary
P.S. Useful books:
Corky Bell, Maximum Boost
Corky Bell, Supercharged!
A. Graham Bell, Forced Induction Performance Tuning