Thanks for some great GTL advice, regarding looking at Gflops.

My findings (specs below) - stable 20x Linpack and 8h OCCT RAM.
Used intelburntest 1.9 at max memory (4GB total - about 3300MB used) in Vista x64 - 2 cycles.

GTL GFlops (x2)
+50/+10 47.0 46.6
+30/-10 47.8 47.8
+10/-30 47.0 47.1

Auto/Auto 47.6 47.8
+20/+20 46.3 46.5
-20/-20 Refused to boot

Now using +30/-10 although it was interesting to note how close auto/auto was.

Andy