My rule of thumb: for sex scenes (well, all the time but MOSTLY sex scenes), unless you’re trying to be funny, leave out “Oh My Gaga” and all variations thereof, including anything involving designers.
I personally am pulled right out of the scene when that’s used and I find it difficult to get my head back into it. I roll my eyes and groan and any heat and tension you were aiming to create in your writing dissipates instantly. And, rather meanly, I feel the desire to pat you on your precious head and say, “oh, honey, no.”
You want to inspire excitement in your readers. Not patronization.
“Oh Gucci” is not sexy. It is camp. So camp. If you wouldn’t say it in bed, don’t make Kurt say it. Please.