Here are two images, one bilinear upscaled from 128x128 to 320x320:
Tthe other is integer-upscaled to 768x768 and then bilinearly downscaled to 320x320.
It looks pretty sharp already. On the 2.8 inch screen of the RG280V it will look even sharper because of the high DPI. You could do this approach for other platforms as well.