In my opinion, any wrx could use a reflash, mainly because they run rich from the factory. WRX ecu's are tuned very conservatively due to the abuse that bad drivers may do to the car. With the mods you listed, i would say wait to get one until you have your total exhaust done and some more engine work, it just isnt worth it at this point, unless you have more money than you know what to do with of coarse.
Overall, stick with a Turbo XS UTEC. You can tune it yourself (with a little training) and you can retune it and download maps off the internet all you want after you buy it, so your ride will always be running to its full potential.
*TBRex* 02 WRB WRX Wagon