spec sirrus upgrade

[kips]

just bought a second hand spec sirrus hybrid for my wife,its a 2011 model
and i got it for 200euro but its a entry level model 21 speed, and want to upgrade
some bits on it,new wheels and replace bits of the groupset.
my questions are
can i put a 9 speed mtb groupset on it and can i fit the 9speed cassette
to road wheels 700c maybe with 25 to 28 mm tyres?thanks for any help.

 

[RecordAceFromNew]

Strange, in that Spesh Sirrus have not been supplied in 21 speed form with 7 speed sprockets at the back for years according to this.

The question is why upgrading to 9/27 speed, is 21 not enough, or is there a problem with shifting, or is lower/higher gear needed? Regardless assuming everything is 7/21 consistent at the moment changing the number of speeds to 9 at the back will require a change in shifter and likely chain too, and if the existing hub is not a freehub then a new rear wheel with a freehub is also needed.

The other thing is Sirrus have been supplied with 700c rims for years. Higher spec Sirrus already come with 700x28 tyres as standard.