Agreed that the "normal" level imprezas (including the sti) are not a significant step up from an LCR - more fun though! (IMHO)
In your situation I would be looking for a bigger leap up. Still since you have raised the question
Cons:
If you live or spend any large amount of time a dodgy area then dont do it - you'd spend all your time worrying about it and your blood pressure will go through the roof!
If you havent got a healthy petrol budget (and a decent source of 99ron) then don't do it - they can be driven economically-ish but when you are having fun then they will drink it!
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problem - ignorant people will label you a boy racer or as someone here put it "scum" because of what you drive. People who know what they are talking about will recognise it for what it is though!. You will also loose all stealth factor - every man and his dog will try it on.
Pros:
If you live in a slightly more rural area or have a lot of bad weather you'll wonder how you ever survived without AWD - a re-mapped LCR might have more power at the wheels but if it cant get down whats the use? I live in the lake district and I would hate to have something powerful 2WD, just wouldnt have the confidence in it!
If you want to mod extensively then the scooby chassis and drivetrain is a great place to start.
The noise - sorry but I love that flat four burble!
Seats - unless you have the Recaros in the LCR the scooby seats knock them out the park!
Image - you are more likely to get someone begging for a passenger ride
Tyres - you might have to replace all 4 at once but you'll do that less frequently then changing the front two on the LCR.
Cliosports and civics are often showing classic imprezas a pair of heels
Might be happening to the badged up sports, poor condition cars and people who cant drive maybe but I've never had problems with cliosports or CTRs even when stock and I'm no driving god!