Originally Posted by
cardew12
In terms of my requirements - I want something quite a bit faster than my existing bike (I'm pretty much cycling in the top gear the whole time at the moment)
Sounds to me like your current Giant hybrid's gearing is too low, causing you to run out of gears.
In that case, out of all the bikes you listed the Giant Dash 4 has the tallest gear combo (52 teeth on the front and 11 teeth on the back), which is a full road-bike gearing setup. You should seldom "spin out" of that gear combo unless you are heading down a very long hill.