I built my own.
First was a 486dx4 @ 120mhz, it even had PCI slots! Windows 3.1 at first, upgraded to Win95 when that came out.
Changed it out 18 months later for a Cyrix 6x86 166mhz quasi-pentium clone, but that thing had so many problems that I changed it out again for an AMD K6 200mhz.
Since the ATX case was a nice standard format, replacing the mobo and/or CPU was only a couple hundred dollars each time. Sometimes the memory was compatible, sometimes not. HDD and optical drive were always compatible.