I think the Sheaffer 444 is the best all-round purchase. It's affordable, can use standard international cartridges or Sheaffer's cartridges or converters, has their beautiful inlaid nib and minimal step which makes it suitable for a variety of grip styles, and a stainless steel body which I find has better balance than the plastic body on the 440 (I love my 440 but something about the balance and/or extremely light weight makes my handwriting worse than with most of my other pens - I still enjoy using it though).
I shall indeed look out for one. Thanks!