Re: Building first gaming PC
it sounds like Silverstone tends to make better quality PSUs. It may not have two 6+2pin connectors but it has one 6-pin and one 6+2pin which is all you'd really need if you wanted that versatility "just in case". I think the only graphic cards that currently need two 8pins are in the $1,000 range or are older power hungry models no1 cares about anymore.
at least 500watts is a good amount to have to as long as its a good quality PSU which it appears to be. even if a graphic cards specification recommends 550-600watts, it really won't need it because most systems don't use as much energy as they used too, plus you'll likely still have plenty of extra wattage room for some overclocking if you ever get into it in the future especially for the 7850 since it doesn't require much power.