hi Migit78 and welcome to EVGA forums.
 
are you going to use watercooling, oveclock the card etc.?
 
here you can see the GTX780Ti models alltogether:
http://www.evga.com/Products/ProductList.aspx?type=0&family=GeForce+700+Series+Family&chipset=GTX+780+Ti
 
generaly the differences are: cooler (waterblock, stok, ACX) and GPU base clock (876MHz to 1072MHz).
additionally some of the components used may be of higher quality for the very top models.
but I think this is more relevant for people doing high overclocking, benchmark etc.

As you possibly plan to upgrade, I would honestly and personally suggest either the 2888 (going to give you the best capability to overclock once you catch that bug) or the 2881/2882. I suggest the two "smaller" cards, simply so that you can save a few AUD and learn to overclock yourself. The ones that are ranged between those three cards are just factory overclocked so that you don't have to. They are lightly binned, so that they could find a card that would run a little faster out of the box and then get sold that way.

Once you get into overclocking, which you will, you are going to want to give yourself some room to play and find a happy medium.

The classified models, on every level, are meant for extreme cooling using liquid nitrogen, dry ice or phase change and that is where they really shine over reference boards. With them, you have to account for larger cards as well, since they are approximately an inch wider and also have more power connections (sometimes) to feed them more juice to get higher overclocks. They are more expensive for a reason. They are meant for the enthusiast builder that wants to come as close as possible to the absolute maximum clocks possible, and they are usually really good at it.

No matter what you decide on, look into immediately purchasing some extra TIM (thermal interface material) to possibly change out if you find the card runs warm. This isn't a huge issue on average, but it does happen occasionally and it is an allowed fix (from EVGA) that is really easy to do. I use Artic MX-4 with good results. Gelid Extreme is another great brand.

Also look at grabbing a backplate meant for your card. The backplate is more of an aesthetic but it does provide support for the card to keep it from drooping over time. That is also not a common occurrance, but it is always better to nip it in the bud prior to needing to scramble.

Just a few months ago,  i was pretty clueless about the different cooling designs and i have learned a lot since.  Maybe this will help you a bit.
 
I've learned very recently about the difference of having good airflow and then maximizing your airflow.
 
My PC was put together by the computer shop and it has good airflow.  I have just enough knowledge, but i have never built one myself.  The case was designed for airflow and it has a front intake fan lower down and rear exhaust fan toward the top(120mm).  Never had heat issues with my 02G-P4-2660-KR (vanilla 660).  Sometimes it was warm inside the case,  but very rarely!  The heat from the card goes out through the slot at the back of the pc and i'll get warm air back there in heavy use.
 
From my recent RMA of the card,  i thought about upgrading and i did take the plunge to the 770 2gb ACX. I picked this one because it was on sale at a local shop.  Did my research and found out the main issue i will have is the heat will stay in the case.  And after a lot of deliberating,  i concluded that i may need more fans and the suggestions i saw talked about having 200mm fans in your case.  Picked up the card and one 200mm fan for $12Cdn.
 
So i installed the card only and checked the heat it was giving off.  I used GPU-Z render test as reference and it climbed to 60c and was very slowly nudging itself up.  I quit the test at this point because it had been so long and i thought it may only go up a few degrees more.  Now when i checked the case,  i could feel very warm air from the side vent with the panel still on.  Took the side panel off and i felt very warm, almost hot air all around the card.  With the GTX 770 topping out at 60c,  i was happy with that and i think other people would as well.  BUT..... I did not like the heat hovering around the card and near the MB/CPU.
 
So after all that,  i finally installed the 200mm fan at the top of the case and it was well worth it.  Using GPU-Z again,  the card got up to 52c and stopped.  It wouldn't budge any higher and i noticed only a little bit of warm air with my hand almost touching the card.  Just FYI,  i am not currently using Afterburner or Precision so no custom fan profiles.
 
So now i understand good airflow and trying to maximize the airflow.  And i feel happier about my purchase.
 
Good luck on your build!