The 7300/7500/7600 are really nice Macs, easy to work in, insanely expandable. I personally prefer the 7300 and (if I need video) the 7600 because they had some kinks worked out of the design, but the 7500 is also very solid. My 7300 has a 800MHz G4, a gig of RAM, an ATI Rage Orion and an OrangePC card, letting it boot OS 9, Windows 95 and Windows 98. Perfect for running all those good old games. 
The only downside is that if you have a lot of stuff crammed in there, heat is an issue. You should hear the fans on the OrangePC and the G4 howl along with the system fan when it's running full tilt. It's no wonder Apple added extra cooling to the 9600.
Also, for many years a Power Mac 7300 with a 500MHz G3 acted as my database server running NetBSD. So that's another option for you.
The only downside is that if you have a lot of stuff crammed in there, heat is an issue. You should hear the fans on the OrangePC and the G4 howl along with the system fan when it's running full tilt. It's no wonder Apple added extra cooling to the 9600.
Also, for many years a Power Mac 7300 with a 500MHz G3 acted as my database server running NetBSD. So that's another option for you.