I've always kind of looked down on systems newer than Pentium MMX and ATX form-factor (getting AT stuff is not hard in Russia). Just felt too modern to me. However, my last Pentium 3/Voodoo 3 build quickly became my favourite machine.

It has an AWE32 with 28MB of RAM, a Diamond Multimedia MX300 and a Soundblaster Live. Also, awesome InWin H500 desktop case, an IBM Model M keyboard and a NOS 17" CTX PR711FL CRT screen. I probably need to get a better mouse and speakers, though.
It's just so convenient! No jumpers, rock stable (it has an Asus P3B-F board) and pretty fast. Just works. I've been playing a lot of late 90s game on it, including Jagged Alliance 2, Sacrifice, Quake 3, Unreal Tournament and Tiberian Sun. Also finally got around to trying different soundfonts, including Chorium, EMU's 8MBGMSFX and others.
I'll probably make a tower case build that will host several ISA soundcards, including Gravis Ultrasound PNP (once I get it fixed), Yamaha SW60XG and MusicQuest clone for my Roland MT-32. It's either going to be a fast 486 build (so that I can run 386-class games on Turbo but also things like Crusader: No Remorse that don't run on P3) or a Pentium Pro. I have a nice Asus Socket 8 ATX board so in theory I can connect two builds using a KVM.