Basicially QPX Express was always a paid and also very limited version of matrix.itasoftware.com
Instead the results were much better (and free) just scraping ITA and being able to enter all those advanced routing codes. Great way for finding error fares, fuel dumps, ... And there was no spam check from google's side, no IP request restrictions, no limit, nothing, whatsoever. The code is a bit hard to go with when they changed to ITA v3 but once you figured it out (and it took us only 2 days since we had a working scraper for the previous version) to adjust it to the new code.