I put the JBL GTO 638 speakers in our 369RL. Like what Chuck encountered, it's a HUGE difference. I am still debating on replacing the head unit with either a real stereo and an inverter or a dual din car stereo and an amp. I will be replacing the outside speakers soon, but I haven't pulled them to see what they are yet.
The stock speakers are 'functional', but not adequate. The magnets are small, there are no tweeters or mids, and the woofers are paper. Nothing against paper cones - my Boston Acousic A200's have them, but for 6.5 inch speakers, you want something more rigid to get the bass out of them.
Thanks
Ct..