The magic keyword here is mipmapping.

Mipmapping increases smoothness and decreases aliasing artifacts if a texture is rendered at a smaller size than its actual pixel resolution. However, even if displayed exactly at pixel resolution, it will introduce some amount of blurryness in Unity. In addition, several parameters influence how a mipmapped texture appears on the screen.

Essentially, you have two options:

• To achieve a crisp rendering of your texture, set the Texture Type to "Advanced", disable MipMapping, and disable non-power-of-two scaling (otherwise you will introduce another level of blurring due to rescaling). The disadvantage is, you'll get aliasing artifacts, if you zoom out.
• To achieve a smooth display of your texture at any viewing distance, enable mipmapping, use "ToNearest" power-of-two scaling (sometimes even "ToLarger" might be better), and set the Filter Mode to "Trilinear" (This is important! Otherwise MipMap interpolation will not work). The disadvantage is some level of blurryness in your texture rendering.

Note also that for certain types of textures, DXT-compression creates heavy artifacts, so you can try to set the Texture Format to "Automatic Truecolor" and see if that increases the readability of your text.

Obviously, you should increas the Max Size to at least 2048, if your texture width is 1700.

what size is your image? have you checked the texture settings? such as texture size and power of two settings in advanced settings?

Edit

have you tried switching off the power of two settings all together as well as switching of mip mapping, turning up aniso level and changing the wrapping settings.

If that doesnt work then I suggest using a texture that is already a power of two such as 2048x512

or

sizing your picture to be of the full screen size then draw your HUD where you want it to appear on screen and delete everything else on it, save it as a png and set it on the HUD to be full screen size.

or

sizing your GUI to be the same size as your picture (1700x600)