There are a variety of differenct benchmarks, but in my opinion the best pure measure of CPU "horsepower" is PassMark's CPUMark. Any other differences in performance are likely due to different graphics adapters; different memory configurations; etc.
For the two CPU's you're looking at ...
A Q8200 scores 3117 on PassMark.
An X4 9150E scores 2137.
I'd consider the Q8200 easily worth the $100 difference.
Different benchmarks will give results in different ranges; but the relative performance of the two is going to be essentially the same. You did just fine with the Q8200-based system :-)
Are there any other notable differences between the two systems you looked at? [Different graphics adapters; different amounts of memory; different hard drive capacities; etc.]