It should be noted that Core Duo and Core 2 Duo are not the same. Core 2 Duo uses the new architecture while Core Duo does not. Unless the price difference is drastic between your considerations, I would absolutely go with the Core 2 Duo.
The Pentium Duo I referred to is not a Core Duo but a Pentium Dual Core[1] "These closely resembled the Core 2 Duo E4300 processor with the exception of having 1 MB L2 cache instead of 2 MB"
We are talking here about a 55€ E2140 vs. 100€ E4300. So yes I would say the price difference is considerable while the difference in performance will likely be negligible in a vdr environment.
[1] http://en.wikipedia.org/wiki/Pentium_E
Daniel