I notice your consultant quoted you a vacuum tube system.  That may be overkill unless you want to store some VERY hot water.

There are three main types of (non-concentrating) solar collectors for water heating:

 - Unglazed (black-painted metal sheet with tubes soldered to it, serpintine or coil of black tubing, or outdoor storage tank painted black)
 - Glazed (ditto under glass in insulating box for greenhouse effect and to keep the wind off)
 - Vacuum-insulated.

Unglazed is for collecting heat at roughly the ambient air temperature, so little or no insulation is required.  Typical use is for heating a swimming pool - bringing it up to temperature after a fill and keeping it warm against evaporative cooling.  The "black tank" is also useful for hot showers in the afternoon and is often used at campgrounds (and typically reserved for staff use B-) ).

Glazed is usually adequate for hot water heating and the like.  You get much higher temperature output because you're not losing very much heat to conduction.

Vacuum insulated is where you pay some big bucks to get extremes of temperature.  It might be good for your stoarge system, since it increases the amount of heat you can store in a given amount of water.  Then again it may be overkill.

If you do go for vacuum insulated collectors, I'd consider glazed also, with the two in series:  Glazed first to get the temperature up cheaply, then vacuum to really peak up the temperature just before the water goes into storage.