I tried a regular filter as a pre-filter once and it was too restrictive. It was a metal one and not the clear plastic so there might be a difference there.
Here's what I'm running now. 100 micron, with cleanable element, and made in the USA! I don't think you'll find a more reasonable price on one it was $27 plus shipping.
http://www.robbmcperformance.com/products/filters.html