Mickindashed is right about some people are using two heat exchangers, it's getting quite a common practice.
The first is known as a SHHE (still head heat exchanger) this not only helps reduce the load on the condenser but also re-heats the returning gasses (remember the GL system circulates the same air around the system without introducing any more), the plus side of this is there's less demand placed upon the heater, so less energy used.
The second is the condenser it's self.
Some of us have made our own updated version of the standard PD, this has four or five cores nestled into a single water jacket, these are known as quad or multi cores.
However I can't find a section for these on the wiki (I'm sure it's there, if not maybe we need to write one).