Thanks for HTTrack. Really great tool.
I have same issue. 
I downloading list of urls > 2000. 
Each page links to stylesheet and js files and also external files.

It will be nice to force httrack loads all page "requirements" and images
before parsing next page.
In that case:
I able to preview first downloaded page now waiting other 2000 pages will be
loaded.

WebZIP had this options called "priority" between loading html or resources