The Q6600 Is going to be a slight downgrade, due to the lower base clock. the 2.4 Ghz chip has better ipc then the 4
On a compute side, once you look at single core performance the 2.4gz chip windws up being worth about a 3.2ghz p4
The 2 chips that -could maybe-
work in an x2 would be
Intel® Core™2 Duo Processor E6850 clocked at 3ghz This would be about a 4.2ghz p4
and
Intel® Core™2 Duo Processor E6700 Clocked at 2.66 Would be worth bout a 3.5ghz p4, but give you 2 cores.
The 6700 i am fairly sure is confirmed working , i do not know if the 6850 works, but in theory it is the best chip you could run down to ipc.
On a compute side, once you look at single core performance the 2.4gz chip windws up being worth about a 3.2ghz p4
The 2 chips that -could maybe-
work in an x2 would be
Intel® Core™2 Duo Processor E6850 clocked at 3ghz This would be about a 4.2ghz p4
and
Intel® Core™2 Duo Processor E6700 Clocked at 2.66 Would be worth bout a 3.5ghz p4, but give you 2 cores.
The 6700 i am fairly sure is confirmed working , i do not know if the 6850 works, but in theory it is the best chip you could run down to ipc.