If You only can update directly to the newest NBU release which is 6.5.4.
Here You will find all needed bianaries for You (I am assuming that Your Solaris 10 is on SPARC platfrom)
Use this page if You need anything else http://www.symantec.com/business/support/downloads.jsp?pid=15143
NB_CLT_6.5.4_326396.TAR - Release Update NB_CLT_6.5.4.tar provides fixes for the Veritas NetBackup (tm) Enterprise Server / Server 6.5 on UNIX clients. NetBackup UNIX Add-on products and Database Agents have separate Release Updates. http://seer.entsupport.symantec.com/docs/326396.htm
NB_BMR_6.5.4_326401.TAR - Release Update NB_BMR_6.5.4.tar provides updates and fixes for Veritas NetBackup (tm) Enterprise Server / Server 6.5 Bare Metal Restore on UNIX platforms.
http://seer.entsupport.symantec.com/docs/326401.htm
NB_JAV_6.5.4_326406.TAR - Release Update NB_JAV_6.5.4.tar provides an update to Veritas NetBackup (tm) Enterprise Server / Server 6.5 Java on UNIX platforms.
http://seer.entsupport.symantec.com/docs/326406.htm
MAPPINGS_6_328211.TAR - Veritas NetBackup (tm) Server / Enterprise Server 6.0 and 6.5 Device Mappings Package for UNIX / Linux 1.78
http://seer.entsupport.symantec.com/docs/328211.htm
NB_6.5.4.SOLARIS_326381.TAR - Release Update NB_6.5.4.solaris.tar provides fixes for Veritas NetBackup (tm) Enterprise Server / Server 6.5 on Solaris SPARC servers. NetBackup UNIX Add-on products, Database Agents and Java GUI have separate Release Updates.
http://seer.entsupport.symantec.com/docs/326381.htm
NB_ORA_6.5.4_326434.TAR - Release Update NB_ORA_6.5.4.tar provides updates and fixes for Veritas NetBackup (tm) Enterprise Server / Server 6.5 for Oracle Database Agent on UNIX platforms.
http://seer.entsupport.symantec.com/docs/326434.htm
If You do need any other agent use the very first link to find it.
*** EDIT ***
Yes after upgrading master server - clients should be upgrded too - this is recommended :D