I think the LS is an amazing car for the money. It is faster than most of it's competitors, and drives/feels great! The 1.8 is no slouch, and there is an emerging aftermarket. I am pretty sure the tune that Trifecta makes will bump you to stock 1.4L levels too.
Now, having said that, how much does gas/range mean to you? To be seriously considering the 1.8 means you aren't interested in the performance aspect of the 1.4, but have you thought about the mileage aspect?
1.8 owners struggle to get 30mpg in the city. They average low 30s on the highway. 1.4 owners struggle to get DOWN to 30mpg in the city, and they average 40+ on the highway.
Just to be nice, lets say you average 6mpg MORE with the turbo. Thats a $225 savings per year in fuel costs. It would take you 132k miles to make up the price difference with the turbo. Throw in a timing belt, you can reduce that number to 96k miles (all based on avg 12k a year)
For some people, the premium isn't worth it. Stick with what you can afford, I guarantee you won't be disappointed.