I always avoid incremental updates and just go with the major release, so that would be MK1> MK2> MK4> MK5> MK7> MK8. MK3 was nasty and just a MK2 with a new skirt. MK6 is really just a MK5.5 and the MK7.5 is a superficial make over too, with a couple of improved mechanicals sprinkled on to make the effort worthwhile.
My advice - get the Edition 30, as late and unmolested as possible. Or keep saving and get a MK7 with the EA888.3 engine in it as it's a proper barn stormer, featuring real VTEC on both cams, among other things.