Is my room big enough for the Harbeth HL5's?

I'd keep the 7es3 and look at upgrading the rest of your system, I've heard 7es3 with tubes and they sounded amazing. FWIW I recently owned, and sold a pair SHL5.. didn't really care for them, heresy I know but that's why we don't just have vanilla..

And I still disagree. The OP asked if they'd work in his room, and yes they would, quite nicely.
Sure, the 7's will show any improvements upstream, they're wonderful speakers. But so will the 5's, and the OP already stated he seems to prefer them.
Everything else mentioned has no regard for context.

When you listened to the SHL5 at Fidelis did you do a direct comparison to the 7es3? I ask because as you say you fell in love with the SHL5, but what you need to keep in mind is that you fell in love with them at Fidelis, in their room, with their gear.. Being as the 7es3 has the newer Radial 3 woofer and is a newer design if it was my coin I'd want to hear them head to head before I made the switch. At least you'd then know what it is you prefer about the SHL5 over the 7es3, or if it's their setup. And FWIW I don't think your room size is an issue at all. I used mine in a room 15' x19 and I never felt like the room was the problem.

I don't want to take this thread too far off topic but can someone explain to me how a smallish, table top sized speaker like the harbeth can be considered too big for any average size room like the one used by the OP?

Please don't take this as being disrespectful as that is not my intent here. I am someone who has full sized tower speakers with multiple 10" drivers per cabinet in a room slightly smaller then the OP room so I am having a hard time wrapping my head around a small speaker like this ever being considered too big.

Thanks