Not worth going for an 08 in a 97 legacy, the 07 STi subframes front and rear will bolt up to your 97 with no issue where as the 08+ is very different and will not bolt up in the rear at all making it not possible to use the rear suspension/hubs etc that is also needed to work with the ABS Canbus system.
Save yourself a lot of headaches and just go 07 Sti at the newest IMO.
Ben