I'm guessing its the original MXT....still a great machine. I would sell the 950 coil and replace it with the Eclipse 5.3 coil.......you will prob leave that coil on a great deal of time for detecting. Is the SEF coil (butterfly) a 8x6 or 12 x 10 ? Ditch the skull what ever headphones and get a real pair. I really like the Whites Pro Stars or maybe a set of Killer Bees. At $550 I think you can do better. The bullseye 2 pinpointer is ok...but ya can get them cheap. In light of the MX Sport release you might see some better deals coming up on the MXT(s) If it is Ebay and you can make an offer, I would offer in the $425 range...if the machine is in nice cond.
If I couldn't get it for that I would move on and wait for the next deal. If it was the MXT Pro or All Pro with the added features, like ground grab, back lite etc then I might bump my bid up a bit.