I went through the same dilema as you are going through. The route I'm taking for my MY00 Legacy GT is the build up of the USDM EJ25.
The main reasons I chose for going this route is:
1) I didn't like the ratios of the WRX tranmission
2) Off boost torque of the 2.0 doesn't come close to the 2.5L
Number 3 is probably the most important reason.
3) I live really close to the best tuner in Canada (www.japanese-auto.com
) and he wants to use my engine as a model. A complete EJ25 buildup with low compression pistons, stand alone Autronic Engine Management system, Maxim Works turbo headers, intercooler, etc. etc. etc. for less than what it cost me for the WRX powertrain that I'm trying to get rid of.
Anyways, I hope I haven't swayed you away from a swap, cause I have a complete WRX engine and tranny, drive shaft, etc. etc. etc. for sale.
On another note, the WRX starts at 227 HP and has proven reliable in hp ranged eclipsing 300 Hp.
WRX engine sale link: http://forums.nasioc.com/forums/show...hreadid=202451