Check this:
http://www.classicmarvelforever.com/cms/benchmarks.html
Class-1000: "bench-press" 250,000 tons
Bench-pressing is about half as effective as dead-lifting. So...
500,000 tons "dead-lift" in HERO is roughly STR 122 [533 ktons].
Class-3000 is only twice as strong as Class-1000 at STR 127 [1067 ktons].
Class-5000: STR 132 [2133 ktons].