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First of all, a quick question: How is a new domain going to influence user experience? Couldn't you redesign the website and keep the current domain? Domain's build up a track record with search engines, historical data is factored in. So yes, you will see a significant impact to your organic traffic. Anytime there is a brand new domain in the picture, you're essentially starting at ground zero. 301 redirects will pass traffic and authority eventually, and as per Gary Ilyes do not lose PageRank anymore. BUT, that doesn't mean you should add a bunch of redirects without a really good reason. I strongly recommend you reconsider switching domain names and simply redesign the domain you've already got.