Nice car!
In terms of bang for buck it's hard to beat a Saab in de UK.
If it's a 2000 model year it'll have the the T5 generation engine, these are bullet proof. But 150 Hp says T7, A T5 version would have 154HP. T5 = Red DI cassette + oil cap above the center of the engine. T7 = black DI and oil cap off-center to the left.
Anyway, both can easily be chipped to 220-ish HP. The T7 turbo is a bit weaker as they last about 150k KM.
If you have a lot of free time, and you can solder a bit and know how computers work you can chip them yourself. I could send you my BDM flasher:
http://forum.ecuproject.com/showthread.php/3267-USB-BDM-adapter-news-and-updates-(part-II)?
There is probably someone on UKsaabs who could do it for a 100 pounds or so. +70 BHP is a nice mod
If you have a T5 engine you'll probably also need a boost control valve, BPC, APC valve)
The steering-brace helps with torque steer, the rest of the mods listed above help a bit overall, but it remains a spongy car, specially the convertible. Replacing the suspension helps the most, eibach spings + bilstein schocks (more than the car is worth?
)
p.s do you still have that photo of your old Saab with the vinyl stickers (specially on the roof)? I'd like to do the same to my locoblade. I want to see what it looked like on your car again.