Since you have a Helix, I would say Silverwing, Majesty, or Burgman 400. The Burgman 650 is huge and heavy and awkward, and much more than you need, even on the freeway, unless you plan on carrying a passenger. I would stay with Japanese because of their proven reliability and parts availability, even though a European scooter would appeal to me more.
2002 Vulcan 750, 2001 XT225
2008 Vino 125, 2009 Genuine Stella
2012 Zuma 125, 1980 Puch Newport moped