Go for NGK; i think we used BKR6E or BKR5E on our 2E before and it worked okay.
What's important is that you just use what is specified by the manufacturer, its gapped to spec, and change as required (i.e. every 10,000kms). No need for platinum or performance plugs really.
If you want more power or response then you can try use a colder plug (i.e. NGK BKR6E), advance your timing a bit then use higher octane fuel (to avoid detonation or tope from the advanced timing).