140mm fans typically run at lower RPM and lower static pressure than 120mm fans. You'd likely see worse temps if this is the case with these fans. Corsair radiators are typically high FPI and require pretty decent fans to make the most of them.
I've been looking to do the same thing to the corsair h100 I have planned for my future build and I've found the Noctua Fan NF-F12 to be highly recommended its not the fastest fan(1500rpm max) but because of its design it beats out corsairs stock fans while remaining near silent. You can easily google up some video reviews on them. However they are not cheap at around 23bucks per fan.