Yes Andrew, you are at the same point as I was a few months ago - Evolution or Enforcer - I went with the Evo because I knew that Alltec wouldn't let me down or make excuses for anything. I'm not saying that Ashbyes would, not at all, I went with the company that supplied my last portable and 2 Tm's and van.
The Evolution comes with 2" hose and as normal is attached to a 1.5" whip line to the tool.
On arrival at the job, you would fill the tank with hot water from the customers hot tap (Heat IS important) and while you set everything else up, the in-tank heater would be switched on and heating the water to around 40degs C. When it has reached this temp, that heater is switched off and the inline heaters switched on, to provide constant hot water as you work. If you stop wanding or whatever for more than a couple of minutes, it is advisable to switch the inline heaters off to prevent them overheating. You are correct that when filling the tank on auto fill from a cold water source, you would have to switch the in-tank heater on to bring it to 40deg C. Hot water cleans better and the carpet dries faster.
Dave.