The cab is indeed awesome and heavy as hell!
I use an ABM EVO III 500 head and it sounds amazing through Ashdown cabs. So to answer your question get an Ashdown head!
Oh and don't get the mag series. They have crap resale value and obviously aren't as good. Can you not save up another couple of weeks or a month whatever?
The boy above is right, get on ebay for a bargain abm head, always loads on there going for less than what they're worth.
Heres an EVO II head on ebay (pretty much the same head as i have except no compressor - its not that good anyway)
http://cgi.ebay.co.uk/ws/eBayISAPI.d...fvi%3D1&_rdc=1