Large (8M) cache vs. dual-core CPUs

I've been given the task of making some hardware recommendations for
the next round of server purchases.  The machines to be purchased
will be running FreeBSD & PostgreSQL.

Where I'm stuck is in deciding whether we want to go with dual-core
pentiums with 2M cache, or with HT pentiums with 8M cache.

Both of these are expensive bits of hardware, and I'm trying to
gather as much evidence as possible before making a recommendation.
The FreeBSD community seems pretty divided over which is likely to
be better, and I have been unable to discover a method for estimating
how much of the 2M cache on our existing systems is being used.

Does anyone in the PostgreSQL community have any experience with
large caches or dual-core pentiums that could make any recommendations?
Our current Dell 2850 systems are CPU bound - i.e. they have enough
RAM, and fast enough disks that the CPUs seem to be the limiting
factor.  As a result, this decision on what kind of CPUs to get in
the next round of servers is pretty important.

Any advice is much appreciated.

--
Bill Moran
Collaborative Fusion Inc.

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