Battery help

[turbo4]

I am running a BL edition revo on (2) 2s maxamps 6000. It has been suggested that I go for 5s instead of 6s. My thought is get (2) 3s 6000 packs then I could run 4s, 5s and 6s (by running what I have now OR one of my 2s along with a 3s OR both 3s together.) Is there some flaw in this thinking? I guess the crux is can I run my 2s 6000 with another 3s despite it being another brand AND may or may not be the same amperage?

For example a 2s 6000 in series with a 3s 5000?