Mixing solar panels

I've imported 2x 300w mono panels from China about 6 years ago and mounted them on my east facing roof. Then added 2x 310w poly panels on my west facing roof. Their voltage specs were close enough as a match and I seem to get some good days between 600 and 800w at peak time. However, I would like to upgrade my panels to a higher watt and more efficient type as my panels are still of those old type. I would like to know what the dangers are of mixing those old panels with ones of higher watts. The logic behind this is to be completely sun reliant during the day with little or no use of the battery, keeping the battery fully charged for evening and night time loadshedding. Can someone lease advise? My battery is a Hubble AM5 5kva with mecer 5kva inverter.