I use a 300x microscope and I have never had any issues viewing very small things like chopped carbon fibers in carbon-fiber PLA. I cannot think of a reason why you could not do it as long as you have a good surface on the part to review.
Eu-Tteum Park Do any of your colleagues have a similar microscopes that you can check out before you buy one? I think 250x should be fine but you'd need to see it yourself to make sure it will be up to your standard. In cases like this, the acceptable level of magnification is pretty subjective.