I'm also going to suggest another 240, but in a roundabout way. How about this for a plan:
Buy / use 3 extra fans and go push / pull. If it does not get you the performance you want then buy a 240mm rad and use two of the extra fans you got for the p/p on the 240. That way you get to try out both options without loosing out on any more than a single shipping charge.
A 240 is going to give you more performance than push / pull. I am not going to give you figures as I don't know enough about your loop; I would be making them up. Try plugging your loop into Martin's pump / rad optimizer
and seeing what difference you get from another 240.
If you can measure the difference in temperature between your water and ambient that will tell you what scope for cooling you have. Realistically you can reduce your water - air delta to 3°C with enough rad, so work off that as a minimum point.
Note that you can
go lower than 3°C delta but you start getting into crazy amounts of rad. I think MartinM210 was getting 3°C with his 2600k and a quad 120...