I have +48 17x8" on my Sti, you will probably have to roll the rears a little, fronts should be fine. You might struggle for shock/spring clearance if you are on the standard shock/spring size. Mine clears with the coilovers with lots of room but would probably need spacers to fit a car with stock style suspension with the extra width.
After seeing the piping, clamps and samco that come in the DSR kits i wouldn't buy anything off them, especially a turbo. It was all complete rubbish. Samco was weak, the alloy was stupidly thin and weak and the clamps were crap. Kit didn't even come close to fitting either.
I'd take an Evo 9 over any Sti. Much better setup to get power cheap with minimal work and excellent turbo on them from factory.
I would rather have a WRX than the Early Evo's but the 5,6 and 9 do it for me.
Mine was doing 4.20 0-60mph on my passport gtimer with my road exhaust, but have removed another 80kg from the car since then and with the race exhaust on it would probably be slightly quicker now.
EJ257/GT35R/6speed would be my path if i was building 10sec GC8.
Budget, probably 25k-30k but depends on how much you can do yourself in terms of fabrication/wiring and tuning.
The main giveaway between the sti -ra and ra would be the DCCD/R180 drivetrain.
My Ver 3 Sti RA has alloy bonnet, guards are steel, boot not sure haven't done the magnet test yet. Manual radio aerial, no rear wiper, quick steering rack, was optioned with electric windows (has stickers over the holes in the door cards where windups were).
No underseal but they do have sound deadening under the carpet.