After looking for the past year on eBay, Reverb, and local listings for an Axe FX II XL+, I've finally negotiated a fair price and am looking at picking it up soon. I'm a bit paranoid when it comes to making expensive purchases (especially when I'm buying something like this used with no warranty). When I see the unit in person, is there anything I should look for specifically so make sure it's in good working order? I don't want to buy it and then realize there's a problem. Any advice would be much appreciated.