Advice wanted
 

Anyone have experince with the JL audio jx360-4 amp?? Good? Decent? Horrible?? Will be using it to power 4 JBL GTO 638's.

It's a nice Amp. The speakers are 2 Ohms, although your amplifier CAN provide a 2 OHM rating for power, I would recommend 4Ohm load, or 4 Ohm speakers be used for best Sound Quality. 2 Ohms will yield higher volume levels, but will NOT sound as "pleasant" as 4 Ohms.

eli47 you can tell the difference in sound between identical speakers from 4ohm-2ohm without any other changing variables including power?

you have special ears

Yes I do and I use QTips on a regular basis, I'd be surprised if others don't hear any sonic difference between 2 and 4 ohm systems.
This brings back the issue that 16 Ohm speakers tended to sound more pleasant.., waaay back when Tube radios were used.
But we're also about to re-open other related issues, so if you have the opportunity to make the comparison for yourself, trust your own ears, not my opinion.

Supposedly the speakers are 4ohms according to the box. Installed the ones in the front door today. Had to trim a little of the door and drill new holes for the screws. My plan was to install the speakers and then take it to the audio guy to put the amp in. Might go with 400/4... Would be nice to have a little extra power... Thank you for the replies

Yes i have used that amplifier and it has these features 3-Way System Protection circuitry (thermal, low impedance, and speaker short protection)
Heavy duty aluminum alloy heatsink for effective heat dissipation
Nickel-plated screw terminals
In my opinion its a decent amplifier.