Need Help Deciding on a Quad KFX400, 400EX 450R

Hey guys, I’m in the Market for a new ATV, I just don’t have too much to spend, $1800 limit. I have a 2001 warrior and when it runs, its fun but, it’s always nickel and diming me. It has full FMF header and exhaust, Wiseco piston, K&N, procom, and more, but it never runs.

The three ATV’s I’m looking at are:

2006 KFX 400:$1700 HMF exhaust, K&N, full skid plates, two sets of wheels and tires, rock nerf bars, tag bar, original owner with title, in great shape.

2001 Honda 400 EX: $1100 All stock wore down tires, original owner with title,

2007 Honda 450R: $1800 has exhaust, all stock, no title bill of sale, just had carb clean at dealer.

So I’m going to be riding mostly trails and doing some light cross country racing with my son. He has a 250EX that we are throwing some 400EX a arms on. I’ve been told that the 2005+ Kawis are fine, they fixed all the frame issues and everything, I know that the 400 EX are great, but I know that parts don’t interchange with the 250ex and the 450R might be too much quad for me, since I’m still kinda new to riding.

Any help would be greatly appreciated.