Hi Linda. I agree with the guys that sites like implantinfo.com can provide you with specific breast implant procedure info. However, the 'girls' there will definitely have difficulty understanding why anyone (like you or myself) who presently has DD cups would like to have them made even bigger! Since I'm on my 5th set of breast implants I can possibly help you from personal experience.
First, as I surmised from your comment, you already know that 'breast lifts' absolutely suck because the surgery cuts through so many blood vessels and nerves. This can lead to loss of sensation and potential breast skin circulation problems on top of the scarring. IMHO a much better alternative (as long as you don't mind the size) is to stuff as large of an implant into the sagging breast tissue as you possibly can! Additionally, overfilling saline bag implants can provide an element of extra firmness as well as tightening up the skin even more due to a larger volume.
It's also unfortunate that many plastic surgeons, for whatever reason, are reluctant to recommend large implants to any woman. However, there are a few 'specialists' around who routinely work with implants over 1000cc. I have personally used Dr. Gerald Johnson of Houston TX, and would recommend him highly, but there are other 'specialists' on both coasts. If you have specific questions feel free to post on my own BBS at http://www.meloniecharm.com or e-mail me.