Which to upgrade first to 6.1 - Enterprise Server 4.6 or B2B 4.0.1

We need to upgrade ES 4.6 and B2B 4.0.1 to webMethods 6.1 (SP1). I would like to know, which product to upgrade first or can select any one in any sequence.

Thanks in advance for your suggestions.

Well it depends on what componenets critically being used there B2B IS or ES.

Start with B2B4.x (IS,TN) and second with ES (use Enterprise Upgrade Utility as told in previous thread)
IS/TN Server with JDBCPools configuration for Database
Broker Server(BrokerAdmin)
Add-on components (EDI,Adapters…)