Not sure how this might apply but I did not have to remove the rear seat only the plastic panne covering the speaker (be carefull you can crack or break off the clips). Then it was just a matter of unscrewing the speaker, I beileve 2 screws. If you stick to a 4x6 it should be a r & r proceedure as long as the depth is good. Anyway I used Alpine 4x6's in mine and was very happy!
If you are running 50rms because of your amp get some better speakers. My Phoenix gold 5.25's are rated at 50w rms and I got them brand new on eBay for something like 34.99 with free shipping through one of the wholesalers. They sound great. I think you shouldcheck out eBay and find some more powerful speakers.