If you kept everything else stock the best capability/clearance and bang for the buck improvement will come from a 2" lift kit. This is because it raises the entire bottom of the machine up. The high clearance a-arms themselves don't provide any lift and thus don't raise the bottom of the vehicle up any. The only ground clearance advantage they have is a little bit where the a-arms angle down from the frame. This does help with getting hung up on the a-arms in some situations but it's not nearly as drastic of a difference the lift kit will make. Where the a-arms shine is they allow you run a larger tire, and thus the larger tire gives more clearance.
Huge difference in costs for the options you mention.
- 2" lift is around $150
- front and rear high clearance a-arms are $700+, and really need larger tires you get a bigger capability increase
- 6" lift is $1,800, but wouldn't recommend this for general trail riding
- long travel kits are getting into the $3,000-$5,000+ range....probably the cream of the crop in regards to suspension improvements with the main downside, to some, being the increased width
Another option that is not mentioned is a shock upgrade to either the Viking/814 or Bandit's. Both brands offer longer than stock shocks which will provide the 2" of lift and vastly improved ride quality and performance. Cost is somewhere around the $1,200+ mark. If you have the money to spend that is the direction I would recommend.