D&D 5E - Arcane Grimoire Too Much?

I need honest advice from DMs who truly know their magic items.

I have a player who's a man after my own heart: he likes to play his characters to their absolute maximum possible effectiveness. In this campaign his character is a wizard, and he has made occasional noises about seeking an Arcane Grimoire, which I regard as one of the best artifacts a wizard can have (short of the really crazy stuff that's impossible to find and costs a true fortune). Now, as far as money goes, these players have done pretty well so far. At the moment, they're L6 and should be L7 before too terribly long.

Would the Grimoire be overpowered for a seventh-level wizard? I mean, let's leave the money question aside for the moment: given wizards' extreme dependence on DC and magical attack stats, would an artifact that permanently boosts one's DC by one (or even two) points be too much? I'm at the point where on Tuesday Mr. Conjectural Me says, "That's way too big a buff," and on Wednesday (same guy) says, "No, it's appropriate." I think the truth, though, is that I just don't know because I've never fiddled with these sorts of items before and therefore lack experience.

Anyone got experience with these things?

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