Construct 2 has a nice option called "Sampling" in the project settings. As Whiteclaws suggested, turning it to "Point" will allow that nice retro pixel look.
When creating the images, don't do a manual upscale (8 pixels for each "pixel block"). Instead, just create each image at 1:1 scale. Trying to do high res images of low res images is a waste of time and resources, both in production and game performance. Only do what you need to in order to reach the result you want.
Construct 2 has some nice options available in it to upscale the screen for you. Under the project settings there is an option called "Fullscreen In Browser" which allows you to set up scaling. These options will automatically upscale the game to the browser's window size (or screen size when the browser/Awesomium is in fullscreen mode).