Why do you need a helical head? Unless you're dealing with primarily extremely interlocked, rippled and exotic timbers they're kind of an unneeded extra. There are some pluses such as easier set-up, quieter machining, and smaller chips but unless you can't spare 10 minutes to set up knives, have terribly noise-sensitive neighbours, and you're trying to cram as many shavings into the dust collector bag I really don't see why a general user would benefit greatly from them over straight knives for the current price point increase.
I'd probably get a decent second-hand model like a Sedgwick MB or Felder AD731 with a 4-knife block either on Tersa or Felder's knife system for less money and use that for now, if you decide that you need to upgrade to a helical cutter head down the line either you can buy a new machine and sell the old for what you bought it for, or both Sedgwick or Felder could supply you with one to fit your existing (and far better) machine, which by that time hopefully they've come down considerably in price. As soon as you buy one of those new ITech or Axminster planers it will be worth about 3/4 what you paid for it as soon as you pull it out of the box, after a couple of years it will be about half.