goodroi - 2:55 pm on Jan 15, 2013 (gmt 0)
When targeting another country it can help to have the website hosted in that country. Of course this does make it harder to handle site maintenance. Most of the time I prefer not to move the sites together.
I assume these three sites are in different languages. I know many people in that area speak multiple languages but I would wonder how much value there is to interlink them since the Serbian speaking consumer would probably prefer content in the Serbian language.
I would also look at the backlink profile for each website. Are they really different and valuable? I would not be too concerned with Pagerank. I would be more concerned with unique domains that are driving referrals to each of the websites.