Although the KingQuad 400 doesn't have IRS and locking diff up front, it is a good value. Note also that the KQ400 is a very "simple" ATV, meaning it's air cooled (does have an oil cooler), and simpler means less can go wrong. The price reflects this as well, and you can pick one up for $4999 new around here (Washington State). The KQ 400 ASI is fuel injected, has an auto tranny with the CVT.

For the cool features (IRS, EPS, etc), everyone is correct that the Grizz or Rancher is the next logical step if you can't find a good deal on the KingQuad 500. Have fun!