You can search for Companies and/or Brands on Winmo based on a spending range at any time. To begin, click Advanced Search on the left side of the screen. Then choose either Companies or Brands.
Scroll down through the Filter Options until you see Media Spend. Click there, and the spending minimum/maximum should appear. Choose your dollar (or pound for UK) amounts in either the thousands or millions and the website will automatically update the results to show only advertisers spending in the range you define.