first, i agree that most powerhouses can move at speeds greater than your average human, likely better than an olympic athlete. but to just say you "think" they should be able to run as fast as several hundred miles per hour is just a thought. certain powerhouses have been gifted with super-speed as an additional gift; most notable among them is warpath, who possesses strength equal to colossus, but is also able to run at speeds of up to 100 miles per hour. he is a mutant with hybrid physiology between powerhouses and speedsters, making him a good bit of both. but to simple stir up the idea that super-strength equals super-speed is unfounded. sure, if you're really strong, you're probably quicker than most; and if you're really quick, you're probably stronger than most. but that doesn't mean the two aren't exclusive gifts, and you can't just "assume" someone can perform certain stunts because of their make-up.
manjaro, you've got your facts wrong. northstar's power has ALWAYS been the alteration of his body's kinetic energies at a fundamental level. as far back as his first appearances in alpha flight, he was hitting mach 10 as a "cruising speed," as was aurora, and on contact their bodies would complete a genetic loop that allowed the release of light. aurora had herself genetically modified by walter langkowski, which made her capable of generating light on her own (at half the intensity she could previously when in contact with her brother,) and also limited her speeds to mach 1. northstar's powers eventually adapted to the "touching aurora makes us stop" scenario, and he was able to create light on his own without compromising his speed. no need to say "HIS POWERS WERE COMPLETELY REVAMPED, AND HE MAY HAVE HAD A SECONDARY MUTATION AND BLAAAAAH!" call it writer's folly, if you want.
quicksilver, however, was only able to hit 175 officially. he performed speed stunts that made that limit seem unreasonable, but there was no evidence to say his powers were enhanced pre-isotope E. when directly exposing himself to the isotope, he was hitting speeds that are superior to how he operates now [his powers settled at an increased level after exposure to the isotope stopped,] but he wasn't hitting mach 10. no evidence to say he was. and, even under the assumption that he was, it still doesn't match the ever-present potential of northstar to hit 99% of the speed of light. northstar is, was, and will be faster than quicksilver in terms of pure speed (despite magneto's opinion to the contrary,) though their powers are vastly different.
again, to differentiate between those who are strong and those who are fast, i could go into depth about muscles. there are two different types of muscular fiber, which need various levels of enhancement to permit different feats. powerhouses get their slow-twitch fibers enhanced to the umpteenth degree, letting them lift incredible weights. their fast-twitch muscles, which specialize in repeated movements without much resistance, may be enhanced, permitting enhanced reflexes (namor,) but that doesn't imply superhuman running speeds. sure, namor can react like a devil, and in your previously-posted scan, he even caught missiles from point-blank range. but his fast-twitch muscles only moved his arms up, and his slow-twitch muscles actually tensed and stopped the missiles dead in their tracks. as a powerhouse, his slow-twitch muscles are much more enhanced than his fast-twitch muscles.
warpath, apparently, has equally enhanced muscular fibers, or at least his fast-twitch muscle fibers are enhanced well past the average for a man of his strength. quicksilver, on the other hand, has incredibly enhanced fast-twitch muscle fibers, letting him pump his arms and legs dozens, if not hundreds, of times per second. his slow-twitch muscle fibers are enhanced to a far weaker degree, though still to moderately superhuman levels.
running requires slow-twitch fibers that aren't weak, but need not be exceptionally strong, and fast-twitch fibers that are strengthened well past the average. lifting incredible amounts of weights requires slow-twitch muscles that can tense and flex under great strain, but hardly requires enhanced fast-twitch muscular fiber... with that simple rational, simple in the sense that it's just anatomy, you can see why most powerhouses aren't dashing from state to state in no time flat...