I have a line on a used Tascam M3500 at a great price in excellent condition. The guys says the faders need to be cleaned, but that's it. My only qusetion is, should I buy it? Are there any limitations I should be concerned about besdides the lack of phase (polarity) switches? I am upgrading from an Alesis Studio32 16 channel so pretty much anything else is going to be better than it.