Thank you very much for creating Qubes. I wish I could somehow support the project more.
The Dell Optiplex 790 is a cheap little box that, when upgraded to an i7 and 16G of memory, seems to run Qubes perfectly with VT-x, VT-d, and TPM support (all three of these options must be enabled in the BIOS).
Attached is the HCL file I created for this box.
I do wish you would create an area on your site for direct submissions, rather than through email.