I wasn't very pleased with the offerings at Motherhood. I guess they'd be much better if you are in the A-C cup size range, but I just couldn't find any support for the DD's... The glamourmom tank was absolutely worthless. No support, flimsy, and it fell apart and go dingy after only a month of wear. I actually threw it away, and I never throw clothing away unless it's literally falling apart beyond repair.
I live in my Bravado tanks, though. They are an investment, but worth it if you can swing the $$. They come sized, like mine is a 36 D/E (to allow for changing cup size throughout the day) and are quite supportive for a tank. Almost as supportive as my one good Anita nursing bra, but still uber comfortable. I sleep in them too.