I would highly recommend that you take a test-sail if at all possible, on both the FX1 and the Inter17 and compare them.
I haven't seen the FX1 here in San Diego, CA, but I have seen the Fox and it did not seem as nice as the I20 (which I have). I have sailed the I17 and it is nearly identical to the I20 in all respects (w/o a jib, of course).
The Inter's are very, very nice boats, much nicer than previous boats I've sailed (several Hobies and Prindles). They have put a lot of thought into making them very user-friendly, in addition to having outstanding performance. After riding with friends on their I20's, getting back on my previous P19 felt like driving a truck in comparison. It took me 3 years of drooling over them, but I finally got one.
Try it for yourself and you'll be convinced too.
Sail fast and have fun,
Alan Thompson
I20 - San Diego