Hi,
If CCDA is what you want, go for it... Groupstudy.com is an excellent place to find others who are going for cert as well.
The CCDA is an equivalent to the CCNA and deals more-so with the design aspects of the network and some of the stuff you learned through your CCNA track. Again, boson is a great resource to have in your arsenal as well as the CCDA book from Sybex, if they have the newer version for the test. Personally, I took CCDA last after CCNP. Learnkey is also a good resource if you have the money and a couple of routers wouldn't hurt. Go to the Cisco site and download the prereq's and know them.