I've seen one STi in Doha.
As for the M3 eater bit, here's a comparison.

STi details
Engine: Turbocharged Flat-4
Power bhp (kW) at RPM: 300(224) / 6000
Weight lb (kg): 3351 (1521)
Acceleration 0-62 mph s: < 5.0
Base Price: 2006 Subaru Impreza WRX STi - $32,995

M3 details:
Engine: Inline-6 (normally-aspirated)
Power bhp (kW) at RPM: 343(245) / 7900
Weight lb (kg): 3415 (1550)
Acceleration 0-62 mph s: 4.8
Base Price: 2006 BMW M3 Coupe - $49,595 / 55,100 €

STi is no doubt a screamer, but I'll take the M every time.