screw the crate. It just sounds weak.
The MG is not a modelling amp, it just has some effects on a knob, you have to spin the knob to turn them on and off. I personally like the MG alot, it has sweet ass crunch with my super 2's, but only one sound... and thats mg sound
I dont know much about the vox, but i've heard both good and bad about it... check it out for yourself.
Spider, yes is a modelling amp, but not all the models are exactly useable. Clean, metal and insane are decent for the price, but the others arent exactly great. Go play one, see what you can make of the different models. Also, the channels are programmable so you can SAVE your settings to each, i.e. save metal to 1, metal w/effects to 2, and so on.
ps, the spider on ebay is a 2, not a 3. the 3 has something like 100 pre programmed settings... that one doesnt.