That article is out of date and a GTX460 is a lot cheaper since then. I have and still own two sli rigs and had two more that I have since scrapped. Going with two GTS450s is a terrible choice in the long run.
Two GTS450's are faster than a single GTX460. I would still recommend just one GTX460, however, to allow a future upgrade path and to avoid dual card setup hassles. If you go SLI, make sure your motherboard specifically states that it supports SLI.
agree with above posts, get the gtx460 and later you can add another one for sli. Never start with an SLI setup, even though the 2 gts450's may be slightly faster in most games.
Or stick a finger up to the naysayers and start off with two strong mid range cards that outdo the flagship card from the get go, then sit back and don't bother to upgrade anything for a couple of years.
Scaling won't be a problem at all with the new gen cards from Nvidia and Ati, but never SLI or Xfire two low end cards.