I did one of my last PA's this weekend with part of the system I sold before building the BF rig (big favour to a friend)
I always ran the titan 48's and DR's using Aux fed subs and crossed over at 80hz. The clarity and depth of vocals, (especially in the lower register) is superb on the DR280's, and as soon as I powered up this weekends rig It was straight away apparant that I was lacking the btm end of the vocals....I was crossing the tops over at 100hz as I did not want to extend them to far.
As soon as I checked the channels out I imediatley put pretty much every channel back into the subs as the traditional tops simply could not handle the low end as well as the DR280's.
If you are running aux fed subs I would be very suprised if crossing over at 100hz does not result in a thin vocal sound.
This is the big thing about Aux Fed subs...your tops need to be able to comfortbaly extend down to 80hz in my experience. Of course you can add channels back into the subs but then you are loosing the whole advantage of aux fed subs...
I did infact have massive satisfaction after this weekend in knowing that what I had built myself (DR280's and Titan 48's) did produce fantastic results, did produce superb low end clarity (which is what I always felt I was lacking).....and built by joe idiot in his garage....

Dave None-Zero has just picked up my Dr's and Titans last week, and I was very sad to see it go, but things change...One thing I do know is that If I do get back into hte bigger PA requirements is that I know the DR and titans deliver in bucketfulls
Dave