I think I tried Faststone some time back and another similar program but since then based on others suggestions here and elsewhere was to try FastRawViewer because it displays the raw file not the embedded jpeg.
It does it fast enough on my quite old PC build and though I find the culling step a tad awkward (perhaps my memory due to intermittent use, the program not my memory, I need to remind myself of the key presses) the speed of loading, viewing, checking stands out and a worthy first step to be really sure the raw is a good 'un
IIRC there is a free trial to see what you think and the cost in the scheme of things is not huge!