Haha...okay that changes a few things then!
Sorry I live in the US (don't throw anything at me please

) and the WRX and WRX STi are different here.
In US dollars, the difference is only about $8000 and not $17000 (I don't know if I should consider that USD or in...Turkey money). Also, in the US, the difference in HP is 73 HP and not 40.
NOW I can see where the real decision making process spices up.
Hmmm.... Now I think if you're going to be economical, then get the WRX over the WRX STi. Save a lot of money for a bit of horses in exchange.
I'm not going to suggest anything anymore since I don't know things so well in Turkey, but I think you're two biggest debates here are:
"AWD sedan vs. RWD roadster coupe"
And if the WRX wins that one, then you've got to decide between:
"225hp vs. 265hp +$17000"