ok so as far i i know only the amd radeon hd 6450 can be crossfired with the A4 Richland.
But i would not recommend doing so as the performance increase will not be satisfactory. i suggest you just buy a discrete graphics card like amd radeon 6670 or 7750 or 7770 depending on your budget and disable the onboard graphics altogether. this would give you much more performance than what the crossfire would give you and crossfire is not supported by many games either so its best to just get a separate graphics card like 7750.
I run a XFX 7850 clocked at 975MHz with my A10-5800K which runs great.
AMD A10-5800K, XFX 7850 Ultra OC Edition 975MHz 1gb, 16GB RAM, Win 8.1 Pro 64 bit, MSI 7778 motherboard, 500W PSU, HP P7-1235, CCC 13.9 WHQL