98-99 are 9.7:1
98 is DOHC and the shortblock might be "iffy"
They are MAF equipped but the 99 MAF is a fragile hot-film type
00-01 are 10.0:1
They are MAP equipped, so you'll need more controls to turbocharge them safely
You will need an uprated clutch, and shift politely or you'll need a new gearbox. It's waaaay to early in the WRX game to know if the WRX's gearbox is notably stronger, how easy/difficult a swap might be, etc.
edit: oh, and 7-10 psi is safe assuming proper fueling and tuning.
[This message has been edited by ColinL (edited April 12, 2001).]