If you find that certain areas of processing really slow down for you in Dynamics GP, consider adding a Process Server. This is just a dedicated machine(s) that allow GP to offload the processing from the client to these machines.
So if you find that AP posting takes forever because of the number of transactions, you can easily setup a process server to process just AP posting and immediately free up the workstation for other tasks.
Setup is pretty easy. You simply install the GP client on the process server and then use Tools-Setup-System-Process Server to tell GP what process servers are available and processes you want to offload to the Process Server(s).
You can have more than one process server and different machines specifications are fine. The process servers don't have to be dedicated machines but it's better if they are. There is basic load balancing and the ability to track start and stop times for processes to improve load balancing.
Often companies have a few spare PC's lying around so if nothing else, this is relatively painless to try. Certainly it is easier than upgrading your server and client machines to better handle the load.
No, Process Servers aren't a panacea and they can introduce problems of their own but it's important to know that Process Servers are an option.
For more information, the Dynamics GP Help file actually has a lot of really good information. Simply search for Process Server and start there.