'....it's better after dividing the big range into smaller ones, to search within those subranges "randomly"'.
That's what I do.... that's exactly how I work..

I'm not a newbie in this matter.... But better with 600 MKeys/s than not looking for it at all... ^^
Yep, and it's not so far fetched either when searching with less power .. i remember someone solving an ethereum block with a very tiny mining rig .. solo