Building a custom made gaming desktop pc, what should my motherboard be? also planning on spending under $800?

It sounds as if you know what you want, but I have a few suggestions. First, unless you already have or are getting the 8800GTX for under $100, get a 9800GTX+/GTS 250. They perform better and are pretty cheap. The 902 is over priced. Get the NZXT Tempest. Better airflow and it's cheaper. If you are using an LGA 775 CPU, then the 750i is a good chipset; I prefer the Asus P5N-D for my 750i mobo of choice. Your RAM won't work. First, you have DDR3 when 750i uses DDR2. Second, it is triple channel, while the 750i uses dual channel. Do not get a dual core! Get at least a Q8400 or a Q9550 is possible. Make sure that whatever case you use has plenty of airflow to keep that hot 8800GTX cool and your PSU has enough clean, stable power to feed that beast. Other than that, it looks fine. Oh, and and don't forget a 3rd party heatsink of you plan on overclocking.