You will probably not be able to get the $750 price point. We can get close, but you will need to make a compromise somewhere in the build given your budget and needs. For simplicity, I suggest a "Core" group of components then decide on which motherboard and CPU combination to put inside later.
Case: Antec Three Hundred Illusion - Inexpensive. It should suit your needs, but gigantic graphics cards may have problems in fitting. $64
OS: Microsoft Windows 8.1 64-bit - You'll need this. It may also qualify you for upgrade pricing when Windows 10 is released. $99
TV Tuner: Hauppauge WinTV-HVR-2250 - This tuner will bring in unencrypted channels, for the encrypted stuff, you'll need a CableCard and a Ceton InfiniTV turner. $119
HDD: WD Se WD1002F9YZ 1TB - This is considered an enterprise drive, but has plenty of space and a large cache. $89
RAM: Crucial Ballistix Sport 8GB (2 x 4GB) 240-Pin DDR3 SDRAM DDR3 1600 - This should be plenty of RAM. $74
PSU: Antec BP550 Plus 550W - Unless you're getting a high-performance graphics card, this should be enough. $64
ODD: LG WH14NS40 Blu-Ray Drive - Per your request. $59
These components should cost $574, the CPU and motherboard warrant further choices.
ASUS A88X-PLUS ($101) paired with AMD A10-7850K ($159) offers a good combination of graphics performance and a reasonable amount of x86 processing capability. You do not need a discrete GPU for this.
GIGABYTE GA-970A-D3P ($89) paired with AMD FX-8320 Vishera 8-Core 3.5GHz ($139) offers good x86 performance, but does not include a graphics solution. You will need to buy a dedicated GPU.
GIGABYTE GA-Z97X-SLI ($124) paired with Intel Core i5-4690K ($219) offers better x86 performance than FX, but weaker graphics performance over the A10. You do not need a dedicated GPU with this.
Ultimately, which one to get depends on where you want to place your money, GPU performance, CPU performance, or multithread performance.