Hello Rod,
Thanks very much for the interest in upgrading.
There are quite a lot of significant enhancements in v7 above v5, including much higher quality audio engine processing (much lower distortion, higher quality filters, etc., all yielding better clarity). The full list of enhancements in v7 and v6 can be found in the v7 release notice here:
https://www.hauptwerk.com/documentation/
I think you would find the audio quality/realism of v7 noticeably and significantly better than v5 (provided that you select the new 'Higher' option for the "Audio engine processing quality" organ preference, which enables v7's highest-quality processing).