I am always watching out for extreme out of footprint reception but up to now i haven't seen a detailed report for each Astra 2D frequency in Beograd. Though some Verticals could be received in Timisoara/RO as you can see here:
_http://www.rdi-board.com/showpost.php?p=371188&postcount=106
There is also the member piratt here from Vidin/BG who gets all the Verticals with his high quality old USSR 1.80m dish. The Horizontals seem to be the major problem in your region. I also guess that you won't have any chance unless trying a 3-4m dish. And even then nobody can guarantee that you will have all the time these frequencies that you might get.
For more detailed analysis if there is anybody in Beograd or surrounding receiving Astra 2D on much bigger dishes than 1.80m please take a look on this local board: _http://www.novisf.com/wbb3/index.php
For the cost of such dishes in Beograd i cannot tell you since i am not aware of the market there. There are quite a lot manufacturers worldwide. Some have stopped producing big dishes others still do. Among the first are for example Channel Master, Kathrein, MWO, Fuba, Siemens, Hirschmann. From time to time you can find them used in ebay or elsewhere. Among the still manufacturing there are professional US imported dishes like Andrew, DH, Patriot, Prodelin, American Antenna. From the UK you can get Precision Antenna, from Finland Aerial Oy, from Russia Supral, from Poland Laminas, from Portugal Famaval, from Spain Tecatel, from Italy Irte, from Turkey Laser. Of course there are some that i am not aware of. The new 1.8m dishes start from about 500€. 3m dishes can cost you up to some thousands of €. The 3m might also have problems tuning in 28.5E if you're aiming at 28.2E because of its very tight reception cone. What you always should be aware of is, no segmented dish but one piece otherwise you risk losing signal if not perfectly installed. If you are interested in making it motorized don't choose the fix mount version. Don't forget that the best dish, especially the bigger, cannot perform at its maximum if no experienced professional alignes the dish with expensive measurement equipment. He of course will also cost you something.