received new drivers from polk

I just recently bought a set of SDA-1C 's on E-bay. The left speaker was perfect it had MW6510 and MW6511 drivers. The right speaker had three bad drivers 1 MW6511, two MW6503,s and one good MW6503 I think, and I called Polk to order new drivers and was told the MW6503 replaced the MW6510. So I bought 2 new MW6511's and 1 new MW6503. Because one MW6503 appeared Ok. But now I have an old MW6503 and the New MW6503 on the same side. They look different and feel different. The other speaker has two MW6511' and two MW6510' s. Did the MW6503 replace the MW6510 one for one?, and do I need to buy another MW6503 so both drivers are the same. The SDA -1c schematic say's the dirvers shoud be MW6510's and MW6511'S. I have powered up these speakers tonight and the two drivers on the left speaker that are the dimensional drivers are distored. Which consist of one old MW6503 from the original speaker, the one that had three other drivers frozen, and one new MW6503 from Polk. Should I replace that driver with a new MW6503. OR Should these be replaced with new MW6510's. that Polk says are obsolete. If the MW6510's are Obsloete should I replace the Mw6510's in the left speaker with two new MW6503's, What exactly is the difference between these two speakers


Thanks,

Bill