no idea what power you will make. visit a dyno, but those additions to the mods you already have will be pefectly safe. it will just breath better. if you have an ems or some kind, you could raise the boost a little, which would help you get closer to the 200 mark. power to the wheels is what matters though... when i dyno'd mine in stock trim, it only put 136/154 to the wheels. i dont think simply bolting stuff on without a ems/tune/more boost would add almost 70 hp =)
and as for the point of twins.. there really isnt a point per say.. much like most of you guys with 300hp single setups have no point. in my area there are way way way too many cops for me be pushing speed even on the empty highway, they just fly over and ticket you. they use drones lol...
doing twin turbo would be about doing something no one really has done before to a car no one really knows about. honestly, it doesn't matter what i do to the msp as most people have never heard of it and will just consider it a pretty yellow mazda protege that i spent way too much money on. not dissimilar to a highly modified civic...
Id see the twins having the benefit of more flexibility. it would spool to stock psi levels quickly, give you low end torque, and maintain that torque over a wider rpm range. a single gt25 doesnt supply the air requirements for the engine above 4000rpm ish but two of them could do the job very easily and would apply the power to the trans much gentler than a big single setup id think.
I wouldn't pay someone to do any of this s*** though. ive always wanted to learn to tigweld. finally i make enough to be able to consider $2000 tools as kinda reasonable, even as a hobbiest ha.