The only reason I wanted my old 1.4 Sport remapped was the fact it (and many other sports) had an awkward flat spot that I hoped a remap would cure.
Looking at it sensibly, if you have the money and the flat spot is annoying you then go for it, it should sort it out a treat. If not then I wouldn't bother, save your money for the next car. The gain you will recieve from the remap will be hardly noticable and it will take a lot of extra modifications to make it anywhere near 100bhp (closed air intake, cat back exhaust, remap, possibly uprated cams). Don't get me wrong, I like your thinking, I had the same thoughts last year, but you soon realise how much it will cost to see a minimal gain
As for not being able to run a more expensive car I think you should seriously look into it, the running cost of my Fab is exactly the same as my old
Ibiza