Hi kamatihno,
I don't have an E series but for a "soft" trumpet kind of sound you van search for
French Horns
Soft Horns
Symphony Horns
Soft Brass
Symphony Brass
Soft Trombones
and of course Soft Trumpet.
For a "soft" Venus kind of sound search for an electric piano sound(EP) like
Suitcase EP
Tremolo EP
For a "soft" strings sound it should be either is as "Strings" either as "Synthstrings"
If a sound is still too "harsh" after applying some effects and changing the "cut off" as DereKa said, then is time to go to the Pad category where all the "soft" but kind of synthi sound of organs are.
So instead of using strings you can use something like LightPad, SoftEnseble,Butterstrings(the butter we eat is soft.... by default
) etc.
As for soft piano kind of sounds combined with a pad sound there are usually sounds called like Sweet Heaven,Dream Heaven and Heaven in general.
There must be something on an E series model from this category of sounds to work with.
Don't forget that you can apply two similar kind of sounds(with proper volumes,panning,octaves and effects) to achieve just one nice sound.
I mean that Voice 1 and Voice 2 don't always have to be two different kind of organs.
Could be similar sounds or even the same sound.(As SciNote suggested)