WRX. It wont take much in terms of modding for it to take the 3. Plus the WRX already has a pronounced aftermarket, as the 3 will take a year or so to have parts that dont cost an arm and leg to upgrade with.
Get an 04/05, or maybe the 06s with higher displacement.
I plan on keeping my Wagon forever, and in the next year or so picking up an STI.
Lets have that precious Mazda3 run a simple Stage 2 WRX and see where it stands
can the stage 2 wrx keep up with a 06/07 wrx with the ej25?