I think the Turbo 2000 started on an R plate 1997, not 100% sure tho, so I'm sure someone will be along to correct me if I'm wrong. It's a UK model, so it will have less power as standard than an import. If you go for one that is MY99, they had very sensitive MAF sensors, so make sure it doesn't have an induction kit on it if it is this MY. Impreza engines all sound like a box of nails when you first start them up from cold, but if this continues as it warms up walk away. Also listen to how the owner talks about it - if they mention warming it up and cooling it down, keep listening, if they mention how fast it is and how great to thrash it walk away lol [] Check all the panels for damage, there's quite a few repaired ones out there as with all cars. At the end of the day if your not happy, walk away and think about it - better than parting with the cash and the engine giving out a week later....
Hope this helps and I'm sure someone can come along and add to this []