2000 Nissan Maxima won't turned over, just clicks

My car refuses to even turn over. It is a 2000 Maxima with 94000 miles. The car was tuned up at 90,000 miles. Ignition coils and spark plugs were replaced at the dealer. I have never missed a service. Before this happened, it turned over very slowly and then started fine. I drove it to Walmart and then it won't even turn over. It just makes a click and then nothing. I turned the key to ignition and unplugged the 40 amp ign fuse in the engine compartment and I can hear a click like a relay being disengaged. I figured the battery died. Luckily, my battery was within the Walmart 2 year replacement period. I got a new battery with 825 cranking amps, checked the fuses, looked at the wires, made sure the headlights worked. Everything looked fine, but still no crank. There was one time that I heard a faint sound like the engine wanted to turn over but it never repeated itself. I am now thinking starter but I have never had a newer electronic car and I need to know if anything else could be the problem. Thanks!