Hi, I have/have had several Markbass amps are are familiar with them, but have a couple of problems and a question on a new amp. F500: I have one of these and like it, but I think it has a problem. After I play it for an hour give or take, it seems like it loses power, the high end diminishes, and all the headroom goes away. It still has a good amount of volume, but it's like playing with a limiter on. The amp never overheats, is only a little warm to the touch. I was wondering if anyone else had this problem. LM 800: I'm thinking of getting one and am wondering about the sound. I know different MB amps can sound different, so was asking if anyone had any thoughts/comparisons of the sound of the LM800? that's it, thanks!