Since you're on
deltaA/deltaX = 2 × deltaM/deltaY
where A is the astigmatism created by the lens, M is the power of the correction provided by the lens, and X and Y are the usual coordinates. Thus progressive lenses always get blurry in direct proportion to the difference between your near and far correction, and in inverse proportion to the vertical distance between the near and far sweet spots.
In practice, some advanced techniques such as grinding both sides of the lens and applying wavefront or raytracing optical simulations can make the problem less noticeable (mainly by moving the worst areas from one spot to another). Some brands of lenses are better than others, and some labs do a better job of making them than others. If you go for progressive ("PAL") lenses, ask to see the "occupational" lenses from several different manufacturers. Learn how to see the "invisible" manufacturing codes printed on your lenses.
My solution at the moment: fixed-distance computer glasses, plus Hoya Summit iQ PAL lenses adjusted to increase the size of the reading zone a bit.