I wasn't knocking iTunes, just saying that imo it's not so hugely better than Spotify that it makes Spotify's SQ seem mediocre by comparison, and I'm surprised that you found it so. I'm personally not a fan I admit; the downloads are of a poorer SQ than CDs yet they are typically more expensive to buy.
You're lucky to have a friend who's so passionate about music that he'll not listen to anything less than FLAC. It's a bit short-sighted of him I agree, but it's one step-up from everyone I know who all think their iPhone slotted into £30 docking-station from Argos is the height of fidelity and anything more than that is a waste :roll:
Good luck with Spotify: I'm a convert who just wouldn't be without it now 8)