I'd stick with it. Napoli and Monaco are both open sides so playing away from home you'd think those games will be fairly high scoring.
I've got a similar cash out for a similar (but slightly higher) return on Chelsea & BTTS No, Bayern & BTTS No, United, PSG, and then Liverpool & BTTS Yes, Real, City tonight. I'm with Barney when it comes to cash outs - I don't see the point of making the bet in the first place if you're not going to see it through bar the odd time you're feeling nervous about one outcome.