There isn't simply one feeling that describes joy or ecstasy. Joy and Ecstasy come in different forms. It's a bit like different grades of happiness. A lot of different things can make you very happy. But only a certain number of the things in life which make you happy will make you so happy that the happiness can't be compared to any of the other things which make you less happy.
The jhanas describe an ascending scale of rapture and joy. But the feeling one "attains" in the first jhana; called "bliss" or "rapture", isn't necessarily anything like the feeling one attains in the second jhana.
The second jhana is defined as a higher type of rapture than the first. This either implies that the feeling of rapture attained in the first jhana approaches a higher intensity in the second. Or else, it implies that in the transition from the first jhana to the second, the type of rapture felt there is replaced by a different type of rapture -considered to be superior than the one felt in the first.
The indication we get about the nature of jhana points to the fact that the types of pleasures felt in each of the first four bodily jhanas are different from one to the other, as opposed to the notion that they are related simply by the intensity of the rapture.
These raptures, and Buddhism on the whole, is about seeking purity and peacefulness, not intense spiritual pleasure. Thus the feelings in each jhana become more and more refined as one travels up the ladder.
For example, the third jhana is described as being neither pleasure nor pain, or above pleasure and pain. This actually describes something. It describes a feeling of such sublime peace that neither pleasure nor pain can give name to it. Equally as untranslatable is the word equanimity. This is the highest of the four material jhanas. Your question as to whether equanimity is a type of rapture that is more intense or "higher" than the previous three is no. It is not more intense per say. It is higher because it is more sublime, and it transcends pleasure and pain, whereas in the first two jhanas the joy of body felt is one of real spiritual elation or excitement (gross feelings of pleasure).
The feeling of equanimity is simply a feeling of peace throughout one's whole body. To name it pleasure or pain would be inadequate. To compare it to the first or the second or the third jhana would also not describe it properly.
The fourth jhana is simply what it is, total quanimity. And similarly, just as space is not the same as consciousness, and just as consciousness is not the same as nothingness, and just as nothingness is not the same as that state called "neither perception nor non-perception", we must try to understand that the fourth jhana and the rapture of the fourth jhana differs in various respects from any of the other jhanas.
Another thing to consider is how inside the context of the "brahma-viharas" we find equanimity. It is interesting that inside the description of jhana, equanimity appears as the definition or the simile for the fourth jhana. Thus one might assume that if he or she practices the brahma viharas, he or she will attain to the fourth jhana just as if he or she were practicing the jhanas themselves, in the case of equanimity.
One has to wonder if the four brahma viharas are similar to the four first jhanas, since at least one of these (i.e. equanimity) is found in both. If this is the case that the viharas are similar to the material jhanas, it would imply that metta, karuna, mudita, and upekkha were in fact simply another way of expressing the bodily or material jhanas.
But that is never stated in any sutta. For it to be the case the four brahma viharas would have to account for all the descriptions of the material jhanas, and there is no extensive or conclusive evidence of this. So we must assume it is not the case after all, and we would conclude that outside of the practice of metta, karuna, mudita, and upekkha, there are four very distinct things called first, second, third, and fourth jhanas (although we can be assured that the fourth jhana is already no different than the attainment of upekkha inside the practice of the brahma viharas).