Hi!

Are these worth re-buiding?

Probably. Even today they'd make decent workhorse systems. I wouldn't spend
a ton of money to make them work again, but some is reasoanble enough.

I thought a Dimension E521 with a blasted motherboard was a reasonable bet
and put the money into a new board. I have not regretted doing so at all.

Did the e series ever have a copper heat sink?

Not to my knowledge. The aluminum heatsink is massive and therefore a good
conductor of heat. In fact, Dell sometimes varied the height of the fins so
that there was an "air gap". And have you seen the front panel fan? It's
massive...!

Wiliam