This was from a recent magazine article, more recent than the Tom's Hardware charts so it presumably reflects SP2 performance.

http://www.gamesforum.ca/showpost.php?p=1823777&postcount=5

Here is the essential information from Doug Horton's article "Maximizing
FSX Performance - CPU or GPU?" from Computer Pilot magazine Jan 09.

He used four graphics cards and one CPU, varying the CPU clock speed.
The CPU was the Intel Quad core Q6600 on an Asus P5E mobo 1066 FSB with
two PCI-e 2.0 slots. The idea was to vary the CPU speed while changing
out graphics cards to determine the limiting factor(s) on framerates
using FRAPS as the monitor. The four cards used were the nVidia 7800GT
o/c, 8800GT, 9800GTX and the GTX 260, all using 178.13 drivers (the
latest available at the time of the article.)

The CPU was run at it's native 2.4GHz speed, then overclocked to 2.7GHz
and 3.0GHz and run with each of the cards at those three speeds.

What he found was that the framerates for the low end card, the 7800GT,
were 15.5, 18.6 and 20.8 fps at each CPU speed.

Moving to the other faster cards at each of those CPU speed gave almost
identical framerates of around 19, 22 and 24 fps on all three cards. So
the increase in GPU power was limited by the CPU speed, and the most
expensive GTX 260 was stuck at the same framerates as the 9800GTX and
the 8800GT due to the CPU speed limit.

You need CPU power, not the most expensive graphics card or SLI to run
FSX effectively.

Good data.

Thanks

Gunny