The new report will not supercede the old report. You can have as many report as you want. Each report cost $180. Just furnish the report that you want to the HDB officer.
I got 2 valuation report prior to my 1st appointment and I used the newer report as I can save a bit more on COV. I did called up HDB to check and they are perfectly fine with either report as long as the valuers are HDB assigned valuation firm.
Hope this little info can help.