A 65W TDP A10-5700 is hardly hot or slow,especially for an HTPC usage. A celeron and a discrete card under a HD7750/GT640 is pointless and I have a Core i3 in my main PC
BTW. A Celery G530 probably has worse lightly threaded performance too,I suspect,so even that excuse is not even valid.
You would need to go beyond HD6570 GDDR5 level performance to get consistently better performance than an A10 IGP.
Not only do you have two sources of heat,you need a bigger case with more fans,and higher idle power consumption too. An A10-5700 based system should consume no more than 30W to 50W for normal usage purposes as an HTPC.