[DarkPira7e]

I hate to be that guy,. but if you can't do it yourself, it costs however much the shop is asking you to pay.
700whp is nothing like 400whp. It requires so much more. Axles, better fueling (including returning it to the tank and probably quite a bit of pieces to regulate and pressurize this system), transmission swap/upgrade, huge cooling upgrades, etc.

Just a transmission to support it will be at least 7-8k, because you'll need to pay labor for install, and buy a clutch to support the power at those levels.
Axles will be another $1000. A differential to put it down (A 1.5 way LSD would be optimal), a wheel/tire setup that can lay it down, ducting so that your cool new cooling system is effective. Not to mention all the custom -AN fittings, lines, all that stuff adds up fast as well.
Maybe you'll need to go with a standalone ECU? There's another 5-10k.

Get it running as it is, and enjoy 400 to 500WHP. You'll kill 95% of the cars you could find who will race you, and you can still replace the broken parts with something from subaruparts.com or O'Reilly's