Prime Haye would be a great test for Joshua. He could evade power shots, counter punch effectively and set up traps. Just the kind of test Joshua needs at this point. He always fought static opponents (or punching bags) and never someone like Haye.
Price is not a good scalp for Joshua now. If he knocks him out we just confirm what we already knew: Price has a glass chin and can't box at top Euro level. What AJ needs is tough opposition that tests him. Takam, Charr come to mind. After that he needs to get someone like Pulev.
Anthony Joshua looks really good. He needs to be patient because when he's ready he'll wipe out the whole domestic scene. Price is a good boxer, but his chin is just too weak and he has poor survival skills. If price gets hit, which he will, then chances are the fight will be over in one or two rounds.
He doesn't need to fight guys like Haye just yet. Time will come though and when it does, he'll smash through them.
Price would be wise to avoid him. Joshua would end Price's relevance and probably his career as well.
On topic, this is a very good fight. Would be awesome to have it on the undercard of Klitschko vs Fury.