I agree that the dual-core Pentium D's seem slow... ArchiCAD doesn't seem to be able to utilize both cores, so unless you're really multitasking, you don't see an improvement. In fact, comparing apples to apples (not Macs), a Pentium IV 3.0GHz costs about the same as a Core-Duo (about the same as a Pentium D) 1.8GHz. I have both in my office (Dells with identical video cards, RAM, and chassis), and I THINK the P4 is faster at rendering and general ArchiCAD use. Going up to a comparable Core-Duo 2.4GHz is an extra $500!!
I'd love to hear a response from someone at Graphisoft. If I do some legitimate speed tests, I'll be sure to post.
As far as the box... I would steer clear of the Dimension series. That's a business-class desktop. Dell Precision Workstations have a lot of intangible speed improvements that are almost necessary for ArchiCAD. I've gotten better performance out of a low-end Precision than a high-end Dimension at about the same price. Put a little cash into a video card (128MB is necessary, 256MB is recommended) and into RAM (1GB is OK, 2GB is better). That should be a good machine.
Good luck!
Chuck
Chuck Kottka
Orcutt Winslow
Phoenix, Arizona, USA
ArchiCAD 25 (since 4.5)
Macbook Pro 15" Touchbar OSX 10.15 Core i7 2.9GHz/16GB RAM/Radeon Pro560 4GB