roland kc550 keyboard amp ,bass speaker choice

[byronboy]

I have repaired a roland kc550 keyboard amp.I only need a replacement 15" bass speaker instead of the blown original,but not sure which to use.The cost of an original is about £130. The spec from Roland just states the amp is 180w rms but nothing about speaker spec.I would look for a 300w rating speaker.Are there
any suggestions for a cheaper alternative that will handle low end keyboard frequencies.
Cheers. Peter.{byronboy]