You need an A/C hasappra....29c ambient seems uncomfortable and not very conducive to OCing anything....Thats rather warm for the GPU...My old 4870 OCed and quite dirty used to get to 82c before the fan started to some funny stuff...it would ramp up and down...and gameplay suffered as a result of the overheat. I suspect at those ambient temps your OC will be limited on any component unless you have some seriously good watercooling...BTW..OP best stress test is furmark and the best bench program is unigine's heaven 2.5
Thanks for your suggestions, but I think I'm fine with 29C and I like it :-). I can't stand cold actually and I live in a tropical country. About GPU temp, I read so many articles about GPU overclocking, as long as it stays under 90C, my GPU will be perfectly fine. My previous build was using HD4850 and because of its poor cooling design I'm only able to OC 5% and its average temp using Furmark is 84C, but it runs perfectly fine after 2 and a half year until now and I'm using it right now. BTW, my HD5850's max temp on Crysis 2 is 68C and HD4850's max temp on Crysis Warhead is 76C.
About dirtiness, I always clean my CPU every 6 months (every part of it including inside my PSU). :-)