The most important thing in a pressure washer purchase is actually the pump, not the engine. Taken care of, the engine will well outlast the pump. So you want to buy the best pump you can within your budget. However, if 299 is your price point (nothing wrong with that), then you might be looking at a lesser quality pump (i.e. one piece, not rebuildable) in which case get the features you want and a Honda engine and be done with it. I saw a Karcher at Costco a few years ago and tried to get some info on how to get parts if I needed to, and it basically came down to the fact that the pump was one piece and was replaceable as one piece. The replacement pump cost 3/4 of the whole pressure washer, so I spent some extra $$$ and got a unit with a CAT pump that is rebuildable.
Ive never tested Costcos return policy on a pressure washer, but it would be interesting to see how they handle it if the pump dies....considering everything has a "lifetime" return at Costco if you are unsatisfied.