That is not where temp should be. Under a full load 56C should be normal, so I assume that it is using a stock fan.
My experience is hot can be thermal paste issue (not enough), or the fan just bad.
I use a aftermarket Cooler Master to keep my APU at 2C at idle and mid 50's when I push all core to 100% for extended periods. Even when I change the Power Profile from Balanced to High Performance.
If you do upgrades to your system I can't believe that would void your warranty. So would be removing the CPU fan and reapplying thermal paste.
If you can't crack the case for warranty issue, then contact them.
I can give step by step instructions for doing thermal paste job.
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