You are quite correct, and normally I would have asked about ambient temps, because there is a huge difference between My constant 71°F bedroom, and the 90°F+ from someone in Dubai. However, with op load at 70°C and idle at 60°C on a stock cooler, it led me to believe it was airflow restrictions, or load would have seen a much greater spread of temp, maybe 90°C or more.
@OP, realtemp readings on an intel cpu are usually very accurate. But it is still software. The readings from Bios are what most experts consider 'gospel', but not at startup where voltages are higher than normal cpu usage. You can try and verify your temps by using 2 or more different programs, but not together as the readings get confused. So while the realtemp readings look very promising, check them against speccy or coretemp, which also run accurately on Intel cpu's. If you get results very similar to realtemp, then you have a good indication that your temps are somewhat correct with those programs.
Once informed with basic info, then decide if the results are good enough or whether further help is warranted, such as removing unused hdd bays from in front if fans would benefit airflow etc.
@Computronix. Wow Sticky! That's a superb article, and my hat is off to you *bows*