I use Principle and Union Central a good bit. They are both great with groups. (Union Central hasnt been mentioned yet, and is a major player in the white collar DI market)
And make sure that all your quotes are comparing apples to apples, its easy not to with DI. And always make sure you put a partial DI benefit on there..
Also, since you have the DI discussion going on with them; I would bring up Key Man DI policies.
Principle has a great Key Man lump sum DI policy. Owners love it.