Dalew

I’ve recently purchased a 2007 wrx hawkeye. the middle and rear is rotten and needs replacing. im trying to find a new exhaust but I’m stuggling to find which one fits. im finding new age, ect but I’m stuggling to confirm what is correct. i know I may need to change the down pipe too as a 3” won’t fit the original centre? Are new age, GD? The same. Are WRX and sti the same? Please help so I can get something ordered! I’m after something like this sub £500