Spk sizing

I know there are a lot of threads about that but those were just confusing me so I thought I´d just ask.
Well, Im going to buy a salomon spk caos and since I read some thread about boot sizing I´m not sure if I chose the right size.
My shoes are size 43, which is a 9 in english sizing and a 27.7 mondo point. My current boots (garmont adrenalines) are 27.5mondo point and I guess they fit pretty well (I can feel the front of the boot with my toes when I stand straight, but not any more when I bend my knees).
Last week I was in my local shop which has the spk chaos in stock and I tried the smalles size they got which was a 28 not thinking about the sizing just to have a look how they feel. In fact I thought they fit pretty well so I decided to order a pair of 28 spks.
but in the last hour I read tons of threads about guys having shoes size 9 and having boots size 26, which let me freak out since I´m not sure any more if I´m going to buy the right boot. Also some guys said that too big boots caused shinbang which is the main reason why I ll buy spks.
so, pleas help me out guys!!!!! I´m freaking out!
oh, I should mention that I have pretty broad feet!
thx