I love the Garritan products even though I have Philharmonik as well. To me each has a purpose. Philharomik sounds "earthier" but Garritan is pretty darned warm and rich to my ears.
I also have Garritan Abbey Road Grand, and I love it, love it, love it.
Garritan Personal Orchestra 5 is superb, and I also own the Garritan Jazz and World Instruments.
This is where BIAB does come into play. I have Jazz Band templates in Aria/Garritan Jazz Band so even when I am using a Jazz midi style in BIAB I run the instruments through Garritan Jazz Band and they sound awesome. Or Real Band, or Sonar. They sound great where ever I use them.
On the first link the first two song used GPO 5 sounds, and the classical album on the right hand in the "more links" columns used GPO5.
https://soundcloud.com/davidsnyder_albumcollectionThis song is GPO5, from a classical album I did last year.
https://soundcloud.com/davidsfilmmusic/first-of-septemberMany of these song use GPO5.
https://soundcloud.com/davidsfilmmusicMy vote is that Garritan is a very affordable place to start and may be all you need for a while.
As mentioned in an earlier post, people are actively streaming the classical stuff and buying it so they must be pretty happy with the quality.
My latest classical album (referenced above) was done entirely in Real Band although I have Sonar and every VST known to man.
All I used was Real Band, GPO5, and two classical guitars, using no effects.