What other surround speakers can I use?

My mains are Eggleston Andra I's I know it's best to use the same brand, but I have a space problem in my new house. The new Katherine on walls, are very large. Any advice out there?
M&K makes a good line of tripole surround speakers that are relatively small. I have been pleased with the M&K SS-150's that I am currently using.
Is this for movies or music? Music is a bit tougher but even so I think you can get away with any speaker you wish as long as its within reason. HT effects are created and ambient and multi channel music for the most part is room fill with exceptions so its not as critical as many would lead you to beleive..........just do what works for you and hell you can always demo right?