recently sold my TSport for a company car.
Unfortunately, havent got long to write masses on them, suffice to say GET ONE!
really miss mine

Awesome car, quick, feel a bit "special" due to the driving position, and if you drive it like you stole it then the performance will be more than enough.
You can get supercvharger conversions for them, but you're looking at like 4k, and tbh it would ruin the feel of the engine probably.
The chassis is phenominal, one of the best FWD habdling cars about probably.
http://www.evo.co.uk/carreviews/evolongtermtests/31672/celica_tsport.html
get the 190BHP, TSport if you can afford it, and avoid the 140 - it quits just when it gets interesting. Well spec'd, you'll love it seriiously - as long as you dont mind planting it into the red line.
There's been lots of discussion about new vs old celicas, and the 190 new is as quick as the GT4 (stock) in everything except 0-60, this is because the GT4 is 4WD (tho there a few that disagree, in purely theoretcial terms its as close as to be no different)