ok, for an SX, 1200 is a good amount, should go any higher anyways....155 for 5 SX's...hmmmmm, aight i guess. BUT, MTX as of a few months ago...I talked to a rep and he said they had only had about 5 returns on the 9500's for blown voice coils....the sub is built like a friggin rock....i dunno if they do re-cones, but unless your sending it over 2000 watts I really wouldnt worry about it.
Plus a really nice thing about MTX is they warranty their subs for 3 years I think.