Can we upgrade the sager np9150 after buying it

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Yes, the parts are upgradable but finding affordable mobile graphics cards is a very tricky proposition, sometimes used ones show up on EBay or something (don't know if they've been fried beyond hope already) but new ones are near impossible. This is the only reliable source for laptop components I am aware of - you can get an idea of the current pricing http://rjtech.com/shop/index.php?dispatch=categories.vi...
I would recommend getting the best graphics you can afford to put in there now, upgrade anything else later...
Just my $0.02 worth

You can upgrade the GPU, The processor as long as the SLot is the same, you can add a mSATA on the newer 9150, and up to 32 GB of memory.