I looked at the spider just 5 minutes ago...
Whadda? It's a digital thingy and they put only four user programs in it??
Didn't really look at it, but this seems a entry level price thingy, about the same as a more expensive model, but some options left out. For example; four programmable channels?? Do they really mean that they just put in 4 user-programmable presets? That has to be a commercial decision. They only need to save a few bytes to keep a preset, which costs virtually nothing in such a design...
So, I wouldn't be too sure about MIDI support... But you should check it anyway. Look at the manuals on their website. If it has MIDI support, you can use any footcontroller... If the controller is just some switches and a jack (marshall type), it is a non digital controller, and you coul look at other brands and try these on the amp...
Hope this wasn't too confusing...