TurboDave went 11's w/ a stock DP, there nice and the car spools a bit quicker and you can feel it in the but dyno but it doesn't compare to 5 more psi+ on alky. Go with SMC.
HTH
THDP will not improve your performance at all, but it would be cool to have a dump you can open when you want to
Get the alky, it will give you 50-75 hp versus about 5 for the THDP at your power level
TH is a nice piece & I could definately feel it on the butt dyno above 70mph - I already had the ATR duals.
The SMC wasn't available when I got the exhaust system, however, bang for the buck would be SMC.
Both vendors are very good to deal with.