I wouldn't compare Nexus with synth1 as Nexus is a rompler (plays recorded samples) and synth1 truely is a synth. Maybe the SampleScience Player would be an interesting option for you to take a look at. There are some similarities between both. Disadvantage: no external control of knobs.
Grand Estate LE runs as a sforzando instrument. So, you have to install sforzando VST first.