PC user here, but yeah it was magic. Installing a new ISA or PCI card was like entering a new world. I remember my first sound card, modem, and 3d accelerator vividly.
Upgrading modern PCs is still fun, but it isn't nearly the same as giving your machine a whole new capability it never had before.
Same thing for us Amiga-owners. While the Amiga had pretty decent sound/graphics-capabilities in the early 90's, expanding the computer with something like a hard drive (which wasn't standard on the smaller models), or more RAM, or video processing hardware, was simply mind-blowing.
1) I overclocked to 25mhz -- I soldered a new crystal on the motherboard
2) Ran in black and white or grey (the graphics card seemed slow)