Upgrade windows server and SQL server from 2008 to 2016 and keeping sage x3 version 6 intact.

I am running Sage X3 V6 and SQL 2008, on windows server 2008, want to upgrade to windows 2016, with SQL 2016, but keeping version 6 intact. Will there there be any problem?

how much will be the cost and time required to perform, how much downtime? any suggestion?