OP seems to have a nearly identical MPS build to mine -- looks just like my MPS 2.5 Powerfactor SS, in fact. The turbo output seems to be very close to my 10cm hta68 (figures below), as were the tuning conditions. My greater output seems to correlate with the extra boost I am running. Dom doesn't like my hta68 very much -- but he's done a damned good job tuning it. He really does like the Blouch turbos. At this point, especially with the 6-speed they just installed for me, my next move will likely be a 20G-XT.
My question for the OP might be why not go bigger than the 1.0?
Shop: Maxwell Power Services
Location: Marysville, WA
Ambient Temp: About 50 degrees F
Elevation: 300 feet
Car: 2006 WRX
Dyno Info: Dynocom
Transmission: Stock 5-speed
Peak HP at RPM: 387 @6400 rpm
Peak Torque at RPM: 410.8 @ 3950 rpm
Baseline hp for a stock Sti on same dyno: 235
Target Boost: 21.8 psi
Target AFR: 10.7
Fuel: 92 pump
Engine/Power Modifications: HTA68 with 10cm hotside installed by Dom, Helix catted downpipe, STi intercooler, Invidia Q300 catback, Gimmick inlet hose, 725cc injectors, Walbro fuel pump, APS Cold air intake, Agency Power UEL header, TGV deletes, Grimmspeed Uppipe, Prosport MBC for hybrid boost control.