I bought my Alienware X51 in 2013, and at the time it was excellent and top notch. Here are the specs:
16 GB RAM, 1TB HDD
Intel i5-4460 CPU @ 3.20GHz
NVIDIA GeForce GTX 750 Ti
Windows 7 professional
Please keep in mind that I am not tech-savvy. I had considered building my own PC back in 2013...