Have you checked for any customer reviews? I would be wary of any that are way off from the others like the $1000 or $5000.... $1000 seems wonderful, but by the end you may be wishing you spent the extra money. References are good, but the same way you wouldn't get a reference from a boss that hated you they are only going to give you the good references.

I have known contractors to purposely bid too high when they really did not want the job. Check the references and reviews of the installers and be sure they are have all the proper credentials - insurance.

I received quotes recently for painting my house and garage. A family owned company that has been in business since 1980 with excellent reviews bid a little over $3000.00 using the Behr Marquee paint that I want on the house. The other company, which is pretty big with commercials and all the bells and whistles wanted to charge me $2550.00 just for my house and $2000.00 for my garage! The large company has to make that type of money to pay for their commercials, advertising, and their fancy vans that have their logo all over them. I went with the family owned company because of the reputation and their no nonsense approach to doing business. They are BBB accredited and a lot more personable than the other company. This could be why your quotes are all over the place.

I guess that does not surprise me. I have had similar experiences with several projects. I will say that sometimes the devil was in the details.

did they list how much that they were charging per cabinet or were the bids just for the whole job with limited details?

in my area, I have noted that the address of the installer frequently explained the difference in bids. that is, the installer or contractor with more or higher overhead costs usually gave me higher bids.

I would check the references and if the lowest bidder has positive references, then I go with it.

Here's my 2 cents worth from 30 years of dealing with kitchen installs and living through the potential pitfalls. By "assembling" yourself, you are leaving yourself OPEN for them to do additional charges during installation. They will blame you for anything that goes wrong. Have each of them seen the exact finished layout? Have they included adding the hardware, or is that falling back to you? Are they expecting a spotless ready to go kitchen when they get there? Are the bids in writing stating exactly what they are doing? Step by step and every line item? Cabinets can get tricky. Many times "spacers" and other pieces might be missing. Your $1,000 guy worries me and your $5,000 guy probably doesn't want to deal with cabinets he doesn't assemble. Have you gotten bids for the installer to assemble and be responsible for everything involving the cabinets? Have you gotten an alternate bid from a local cabinet shop that fabricates and installs cabinets in a similar style to the IKEA ones you selected? With that option, you will have more of a warranty, should anything go wrong. Are the installers recommended by the IKEA Showroom?

You didn't mention how many cabinets

If you assemble them yourself [and you're handy] it will take you about 45 minutes to assemble the first one, but then you'll crank the rest out at twice that rate

the complications cost the time, if the water in and out is straight out the wall and not running behind the cabinetry, if the electric & gas outlets are in the right place for the appliances, etc., if the floor is level, the walls are true, the corners are 90-degrees :)

it is a good idea to make sure that the appliances are a serious consideration when positioning the cabinets [a pain to re-shuffle if not enough/too much clearance] and the counter top/work surface needs to be considered as part of the package otherwise you'll just be deferring problems

if you like the $1000-guy ask him why he is so cheap :) -- the pack at 2-3k seem to set the pace -- in any event, choose someone you WANT to work with as it will not go smoothly [no really] and problem-solving is the key to a successful install every time

Good Luck :)