Have looked at something like this myself.
IIRC, and this only applies to Hirsch upgrades, the 150 bhp can be increased to 195bhp (which I have and is great fun!), the more powerful 175bhp can also be increased to 195bhp. So not as wide a grin! Neither can be a straight ECU upgrade to 210bhp (or beyond) without other amendments I'd guess, I've not looked into this.
There were some "half price" offers for older years on the above, like £399 instead of £999 (plus vat?), can't remember but you'd need to check with a Saab Hirsch specialist for what a specific model year can have.
Hope that helps!
Terry