What engagement diamond/setting with 5 stone wedding band?

[diamondsareagirls]

I have a 1.50 ct 5 stone wedding band. What would be a good sized diamond on the engagement ring to look good with it? Also, is there a particular Whiteflash solitaire setting that would look (the 5 stone is their U prong one and my upgrade diamond will be from them).

Thank you!

 

[diamondsareagirls]

Would a 1.60 be overwhelmed or look funny? Is 1.80 better?