Yes, you can use a Marshall amp with a Mesa cabinet as long as you make sure the impedence matches, i.e. 4ohm amp with 4ohm cab. Midi cable is not the same as instrument cable. A power conditioner is not much different than a surge protector/power strip. I would still use the DC Brick. Feel free to use www.google.com to search for this stuff anytime. It's quite easy to find some of the info you seek.