I'd be all over Barella as his replacement. I've been a fan for quite a few years; he has a bit of everything and has that bite, which a lot of top players lack nowadays.
You'd like to think Lukaku being at Inter would help us as a bargaining tool of sorts, but his loan so far hasn't been good at all.
Having said all that, I wouldn't be surprised if we went for the former for obvious reasons & potentially a few other Brighton players (Mac Allister is someone that could be a good fit down the road).