Deanne: I admire your diligence in getting the BK7m to work with your T4 setup,
but for me, Tyros 4 alone delivers it 'all included' in one unit, including the quick setup time.

Deane, what specific Roland sounds or styles are you wanting that's not included, or can't be closely duplicated on the Tyros 4 itself?
Because many of Roland's sounds are available as digital samples (vst, akai, etc),
you might consider using Extreme Sample Converter to convert these to Yamaha TVN/UVN format and then load & play them in your Tyros 4.
If it's specific Roland Style(s) you're wanting, these too can be exported and converted to Tyros 4 '.sty' format.
Just my idea of of a way of maintaining the ease of a 'one unit' system, including the greater ease of storing & calling up everything in Reg.