We have gone round and round on this subject in one form or another. What is comes down to is what you can live with. GM is so subjective, what sounds good to you doesn't sound good to me. If you are preparing this piece for live performance, I'd be willing to bet your "non-musician" audience won't notice or care. We are always our worst critics. I'd did a gig last night with a kick-ass singer who uses all mp3's. Most of them sound good but some are really bad. I've heard better Gm files than some of her mp3's (in my subjective opinion) But she is such a phenomenal singer, NO ONE CARES about the so-so backing tracks. Now I know there are plenty of people out there ready to beat up on me for that statement so have at it. We've been down this road before and will again, and again etc...I know many of you do this just as a serious hobby or for the joy of it and want to obtain perfection if possible. But as Mac stated, to get the desired results is not worth the time and effort. BIAB is my vehicle to get paid. Time is money, I'm always balancing the time it takes to get the song right against what ever else I need to get done during the day. To get the midi sound you are looking for I think you will definitely have to go with one of the external sound modules that has already been mentioned. Good luck to you!

Dell Studio 16 Laptop i7 with 256 gig SSD
BIAB, Reaper, Encore, Sibelius
Roland SD-50