Sure, if you have the technical skills or are considered a high value target by your hosting service(!) then I guess you don't have a problem.
The only services I know of that can stop a true DDoS attack are Prolexic and Gigenet. If you have names of other services or hosting providers who do the same, please let me know.
Preventier is not part the basic Rackspace hosting service. It costs $5000.00 just to setup and they make no guarantee. Again, if you know of a hosting service that provides DDoS protection as part of their basic service, I'm all ears.