Been trying to research what my next detector will be, not much info (except from one online source) on the difference between the two. Between the two, the cost difference is no issue. According to what little info I found, the older model goes deeper but the newer model was quieter but not as deep. Anyone use the two? Was the old version noisy? The 4000 were very quiet in WA, so I would think the 4500, even the early ones would have been just as quiet?!