How far can I resize a x264 video without blurriness?

I have an x264 video at 700x400 encoded at 1400 Kbps with High Profile Level 3 which I want to play at 1366 x 768 screen resolution. How far can I change or resize the video player window without noticing an quality degrade in picture? I suppose the bit-rate should tell me but I am not sure. The quality is far more better than DiVX video which gets blurry too soon upon resize.