WHEW! ...Been there with sports bras. I'm pretty heavy-chested/full-breasted. For regular bras, I buy bras for the cup and modify the bands for proper fit. (Thank goodness Mom taught me how to sew!)
Anyways - the absolute best sports bras I've used invested in are Enell brand bras. Well worth the money, and can last a very long time with proper care and rotation. The way I see it, I save on not stretching out my 'regular' bras, not having to buy a ton of 'trying-to-accomodate-larger-sizes-but-not
I've worn Enell sports bras for more than 12 years and they are exceptional. I have done cardio kickboxing, HIIT training, Stairmasters, elliptical machines, jogging, moving people in/out of apartments..Well, you get the picture - wearing Enell bras.
BTW - you may have wondered about what bras of the 'larger chested' ladies on the Biggest Loser were wearing. Yes, they were Enell bras.
~Dhamana, a.k.a Dmshaykz - not a spokesperson, but an avid fan! :)
p.s. - feel free to send me a message if you have questions. www.enell.com