Did you mean 5D4 ?
In any case, if you are concerned about SNR, even an old used 5D2 will be better than your 7D.
Not much of an upgrade, and a downgrade in some ways. I used both at the same time, and the 5D2 had more banding noise in many cases, and a crop from the 5D2 looked worse at all ISOs, despite having lower area-based high-ISO read noise. The first two 5D-series cameras had poor noise character.
The 7D(1) and 5D2 are both avoid-cameras, though, if base-ISO DR is important; they have issues beyond what DxO and PDR charts show.