The tweeters are not 100-200 watts, no way, no how. They may be rated to work with speaker SYSTEMS rated at 100-200 watts. This is a common misconception with tweeter marketing in general.
Have you considered a used (Genz Benz) NeoX or Uber 212, both 4 ohm cabinets, a little heavier than your goal but meats the low and loud part. You should be able to find one in your price range as well.
I think you will have a hard (read as impossible) time finding any single driver speaker in the 500 watt (real, "RMS" or continuous average power) range for that kind of money. Even without a limit they are pretty darn rare. Be sure you understand how the ratings are made. Your amp is rated at 600 watts RMS per output channel, be sure that your speaker is rated for around 500 watts (or more) using the same "RMS" rating.
Note that "program power rating" of a speaker is typically defined numerically as 2x the RMS power, and peak power is 2x the program power or 4x the RMS power of the speaker. With amps, peak power rating has a different meaning, which is typically 2x the RMS rating of the amp. Your amp is rated at 600 watts per channel (RMS) and ~1200 watts per channel (peak). Be sure you understand how these units relate. I generally recommend a maximum of about 1.5x the RMS rating of the amp, and IMO between .75x and 1x the RMS rating is generally safer.