The Bulgarian web hosting company, which can be claimed as the largest in Bulgaria, definitely is Superhosting BG. Unfortunately, thir price is a little bit high. I hosted there some of my websites, and still did not get any problems with support, or bandwidth. Their speed is quite high, but really the restriction of Bulgarian Language maybe will stop their work in the borders of Bulgaria. You can test them, because their service is not bad, but definitely I hate the restriction of 4 websites, which can be hosted there. Each next website is paid and the price is getting high. There are also other offers for services, just like additional IP Addresses and Free Space.
The Bulgarian Leader Superhosting