The estimated 2000 samplerate would have to be adjusted to produce 4:3 image in the 1600×1200 active area, can use the BIOS screen for that.
The higher sampling rate will certainly help the native 720 horizontal resolution pixels look less deformed than they are in Line2x.
Thank you very much for looking into that Marqs.
EDIT: Yes, you are absolutely right, I take my words back.
My video cards produce different pixel clocks for 640×400 (800 sampling) and 720×400 (900 sampling).
All games that I tried output 640×400.