A PS on MIDI strings. Strings in an orchestra often sound that good due that the players adept their fine tuning according their feel of the scale's tonality. Usually if i have the time to check matters in a midi controlled environment, i'd like to fine tune the 3rds and sometimes 6ths for a more natural feel. Hardware synth or VST. You can't do that with real tracks.
With them you might be best off to use those in the key where they were recorded in.

F.i. a cajun melodeon is tuned to 'just' tuning. Played latter instrument at a studio job, and the engineer, a well trained classical pianist with ears used to his concert piano's tuning, said: argh, that thing is way out of tune. Well Marc Savoy himself tuned it, and he's the (cajun) expert and one of the best tuners around: 3rds and 6ths are 15% lower, but i changed it later towards around 8 % below zero. Less chilly and chicken skin for a few eager ears i guess LoL. -F