Why not stay with VN? You have 10 of the 12 segments domestically plus at least 4 more for Orlando, so you have silver without any change of habits.
OK Plus (Czech) has a lower than average requirement for status, 15 segments for Silver or 30 for gold (ST+). There are some major changes occurring there as well so research before jumping in. Big mile bonus promotions seem to be the domain of US and UK carriers so I would suggest Delta if that has a lot of weight.