I want to build a new desktop PC for MD simulations of relatively simple protein/carbohydrate systems using mainly GROMACS and Amber force field. No ab initio or QM-MM simulations are intended for now. For instance, I have been working with a protein of approximately 1500 atoms in the presence of small carbohydrates (<100 atoms). For the protein alone, my home PC (i5-4570 CPU 3.20GHz, not GPU-accelerated) does approximately 5 ns/day, so I want something considerably faster than that.
Which hardware should I choose? Could you suggest low (800 US dollars) to high (2000 US dollars) price configurations with good power considering the current technology available? I am not sure if I need a GPU-accelerated machine, so I am open for different configurations.