Screaming Frog's a great one, a few Google Chrome plug-ins I would use are:
ReDirect Path -> https://chrome.google.com/webstore/detail/redirect-path/aomidfkchockcldhbkggjokdkkebmdll
Check My Links -> https://chrome.google.com/webstore/detail/check-my-links/ojkcdipcgfaekbeaelaapakgnjflfglf
If you use these in combination you will hopefully be able to find any errors in your new design.
