Not sure of the water resistance spec of your edition of the 405. Garmin's latest, smallest, cheapest GPS running watch, the Forerunner 10, suprisingly has a better waterproofing spec than the others up the range.
My understanding is GT-2170s are one of Asics go to cushioned support shoes. The other is the Asics Gel Kayano. 200 miles is towards to the lower limit of the life expectancy for the cushioning of a running shoe, but it depends on body weight of the runner (and presumably how their foot lands) as well as the make of the shoe. The colour of running shoes seems an issue for some and not others. I'm in the camp that finds it a pity when a shoe goes into a new version and the colour schemes are terrible. The unpopular colours usually end up a bargain though.
If you need the HRM, try to get a deal on the FR110 with HRM package. £120.99 on Amazon according to the Garmin running watches page I maintain. (If you buy separately, it looks like £30 to £35 just for the HRM.)