JBL marine stereo equipment is actually produced by a company called Prospec Electronics. They license the JBL brand and their production is completely separate from the main company. Prospec has a very tight focus on marine stereos and they are very good at what they do.
The JBL speakers they produce are a good mix of quality and economy. The MS6200 6 1/2″ round coaxial speakers offer sound quality similar to many higher end products, but only cost around $120 for a pair. They are also very durable and can easily handle rain and splashing and even getting hosed down from time to time. They can handle up to 60 watts RMS and 180 watts peak each.
The MS9200 JBL speakers are 6 x 9 oval shaped and they are built to the same quality standard, but with even better power handling. These can take up to 100 watts continuous and 300 watts of peak power at any given instant.
On the lower end is the MS6100. These are dual cone speakers so they don’t have quite the frequency response of their more expensive brothers. However, the sound is quite decent for a speaker with no tweeter.