[chris lewis]

I have viewed thru a 12x80 Vixen during day time testing. The image was very sharp and contrasty. It was sharp to 90 %. They are very well built hi- quality binos [Japanese made]. They have multi coatings 'only' - not 'Fully multi coatings' - however the coating were very impresive and did supress internal reflections very well.
Some issues to consider - the exit pupil is 6.7 mm so these size binos are best on very dark skies and with 'young' pupils that dilate that far if not you will waste light.
The Afov is 54.4 degrees - not wide by any means.
I have 3x 80mm size Japanese binos - 11x 16x and a 20x. [Non vixen]. I use the 11x one the least - this is primarily related to the narrow Afov
Viven make 3 sizes 80mm binos with different mags. the 12x, a 16x and a 20x - the 16x has a similar Afov as the 12x whilst the 20x has a wider 66 degree Afov. The exit pupils are 5.3mm [16x ] and 4.0 mm [20x] which may be more suited for your eyes and viewing conditions.
The other consideration is the mount - at 2.3 Klgs. they do require a suitably tall mount and safe [!] mount - even at 12x. I do occasionally hand hold my 11x for short periods only however.
If you have your heart set on the 12x fine - however I would strongly suggest you view the 16x or the 20x binos as well [if they are available] they do provide a better image scale and the ability to see 'deeper'.
There are other well spec'd Kunming binos in the 80mm and 100 mm sizes from AOE / Andrews etc. that are less expensive that you may also want to consider - just avoid 'paralysis by analysis' !
If you do go for the Vixens [of any size] you will have brougt very hi quaity binos that will last a life time.
Just some thoughts.