Rena Filstar XP3 - larger o-rings?

[jawn_nm]

I got a Rena Filstar XP3 thrown in with my 75G tank that I'm setting up now. I'm planning on pretty heavily planted with some fish (not a ton, but maybe ~30 inches?). I'm using a Hydor in-line heater and a Rex reactor for CO2. The filter ran fine for about a week before I added the reactor and heater, but now it leaks out of the power cord hole after about an hour. I replaced the o-rings on the quick disconnect, and re-greased them (and the rings inside the disconnect too). It ran for about 5 hours and then started leaking. Anyone try using larger o-rings to stop the leaking? I'm ready to just bag this filter and buy another one (Eheim 2217?) but I thought I'd give the Rena one more chance!