Are you using just RealTracks in BIAB or MIDI or a mixture? I take songs into Sonar from BIAB and I always replace the drums - I often like the hits and fills but I really don't like the sound of the kit used. If you're using RealTracks:- You can actually have your Sonar project and BIAB open at the same time - resize the windows so they're side by side - and if you've got a current version of BIAB you can then simply drag each instrment track over into tracks in Sonar (see button top left in BIAB). These are WAVs. If your BIAB song has ok MIDI drum beats then export that as a single MIDI track and import into Sonar, where you can tidy them up/improve them and use I drum sampler to make the drums realistic. I most often use XLN's Addictive Drums which I think sound great. MP3s don't figure in this. Let me know if you need any more help.

John

Songs web site
YouTube Channel
BIAB 2019
Cakewalk by BandLab
Studio One 4