You should certainly add the extra memory. With three memory modules installed, the controller will be running asymmetrically, which will slow things down. Make sure that the memory module you buy matches the other three exactly.
Once you have got your memory sorted out, you should do some benchmarking to establish where the bottlenecks in your system are. I'm no gamer but I would think that upgrading dual graphic cards on a mono-processor system is not going to get you very far.
You might want to look at getting an SSD drive. Even if the CPU is struggling, it will be able to pull stuff off the disk faster. This may give a significant improvement if the software is paging owing to lack of memory. You should do some system monitoring to see if this is happening.
Finally, are you gaming on-line? If so, is your internet connection fast enough for your gaming software?
'Sir, please,' she said ... 'Will you not share your wisdom with us?'
'I have no wisdom,' he told her.
'Your experiences, then?'
'They have been trivial, uninteresting, and full of error.'
Ian M. Banks - Feersum Endjinn
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