I would trade in the Emperor and/or get a filstar xP3 if you are going planted. I really don't think two filters are necessary for that tank. With an xP3, you would have a 7.6x turnover rate which is good for plants and delicate fish like angels.
Honestly, I definitely see a slight difference in p.h. ever since I replaced one of the Emp 400s with an xP3. Less surface movement and therefore less CO2 gassing off.