For cooling a 030 I would get a old northbridge cooler. You might have to cut it some to make it fit. Also a laptop style 20mm fan should be enough to move some air.
Regarding newer systems(x86). The latest p4 series require extremely much cooling. The require coolers that can handle 100w+. You don't have to go water cooling though.
The newer AMD systems(a64) however are easier to cool than the old XP series. But good cooling is always needed today.
I remeber reading somewhere(think it was tomshardware) that they tested if a modern cpu(athlon 1200mhz at the time) could handle boot without heatsink. They some laser thingy to measure the temp. 1-2 secs. after pressing the powerbutton the athlon reached 300 degr.(C) and the cpu died(probably long before it reached 300)...
