Hey Denise,
I havent grown too many doubles, but my favorite double CV is Heaven's Scent. It has a nice full bush and nice bright ruffly flowers. Its nice also because it blooms as both a double and single depending on the weather, so you can have both! It is also occasionally scented.
Another CV that is like this is Love Story, great bloom and awesome bush. Both these CVs get their great bush and bloom from their parent Rosalind, which is another great one. Rosalind is an awesome CV, but unfortunately must be grafted so there aren't too many of them around. There are several other CVs that are doubles which share Rosalind as a parent and are really nice others that come to mind: Fat Actress (red/orange), First Lady (bright pink) Las Vegas.
There is another group of nice doubles which come from Stormy Days, include Lady in Waiting and Her Majesty.
The newest batch of doubles released this and last year mostly shared Standing Ovation as their parent, this gave large orange and yellow type blooms, Samba Dancer, Bedazzled, Hot and Spicy.
I also asked a similar question a while back and you can find the post here:
http://www.hiddenvalleyhibiscus.com/forum/index.php/topic,101.0.htmlFinally there is one double that I am looking forward to being released that Charlie nicknamed double Vin E, which I think was Midnight Blue x Allure. That one is one to look out for!
Hope this helps