You'll find a modest, but noticeable difference in power with an intercooler fitted.
With a constant pressure, air at a low temperature will have a lot more molecules present than air at a high temperature. A good front-mount intercooler should be able to drop the temperature from about 200C (post-turbocharger) down to around 50-60C. The temperature will rise again as it enters the intake manifold and into the cylinder - but not by much until the intake valves close, and by then it's all extra bonus combustion power.
In short, get an intercooler - it will help greatly. If you don't like it for the performance gain (which in real terms isn't going to be huge, but it will be noticeable), you'll love it for its ability to catch parts of the turbocharger compressor when it lets go and they start heading for your intake manifold!