Fixing slightly fuzzy screen captures

[Ayanefan]

Tools used:
AVISynth
Photoshop 7.0
Premiere Pro 1.5

I've been doing a lot of screen captures from AVIsynth and pasting into Photoshop, removing the background and then adding them together in Premiere with background but have an annoying issue that everyone that does this must have seen.
Some scenes that I wipe the background to keep the character visible have smaller images in them. When I add them into a scene in Premiere, I sometimes need to enlarge the image slightly to get the correct size ratio with the rest of the characters that I have added in. The problem is that when I enlarge the image, the character becomes slightly fuzzy.
I've tried to fix this a few ways:
-Modified the image in Photoshop to add DPI (but this is almost impossible as adding dpi to an image that is 72dpi doesn't work all that well, the image is still pixeled at 72dpi and becomes a high-res jaggy if enlarged, even with unsharp mask and despeckle)
- Brought in the image in Premiere and tried to use a video effect to fix the issue (sharpen, blurring... oh gosh, others too but I can't remember because I'm at work).
In any case, what would be the best way to try and match the clarity and/or resolution when an image imported into Premiere is fuzzier than other images in the same scene?

Whew! Thanks.

Ayanefan.

[Scintilla]

Try using one of the sharper resizers in AVISynth to do your resizing before taking the frames, such as LanczosResize or Spline16Resize.