According to the message included in c2dm website it seems that cloud to device is not supported anymore. I know that it's clearly specified there but, just to clarify it one more time (cause I really need a new user), is there any possible way to obtain any new senderId/quota to operate with c2dm?
No, you cannot get senderids or change your quota any more. C2DM has been completely replaced as of today by Google Cloud Messaging.