How can I lower the cost of my gaming pc (with monitor,mouse, and keyboard) to under $2000

Solution
This is an edited build of yours to make it slightly cheaper only.
PCPartPicker part list / Price breakdown by merchant

CPU: Intel Core i5-4690K 3.5GHz Quad-Core Processor ($224.99 @ NCIX US)
CPU Cooler: Cooler Master Hyper 212 EVO 82.9 CFM Sleeve Bearing CPU Cooler ($29.98 @ OutletPC)
Motherboard: Asus MAXIMUS VII HERO ATX LGA1150 Motherboard ($199.99 @ NCIX US)
Memory: G.Skill Ripjaws X Series 8GB (2 x 4GB) DDR3-1600 Memory ($79.98 @ OutletPC)
Storage: Samsung 840 EVO 120GB 2.5" Solid State Drive ($84.99 @ Amazon)
Storage: Seagate Barracuda 1TB 3.5" 7200RPM Internal Hard Drive ($53.98 @ OutletPC)
Video Card:...
Change it an i5 if it s just gaming. Sabertooth is an overpriced motherboard where you can probably get a Maximus for a cheaper and better features like integrated sound card is much better and clear. Will you be streaming and recording?

Anyways there is a few things. I'll be back with the new build.
 
This is an edited build of yours to make it slightly cheaper only.
PCPartPicker part list / Price breakdown by merchant

CPU: Intel Core i5-4690K 3.5GHz Quad-Core Processor ($224.99 @ NCIX US)
CPU Cooler: Cooler Master Hyper 212 EVO 82.9 CFM Sleeve Bearing CPU Cooler ($29.98 @ OutletPC)
Motherboard: Asus MAXIMUS VII HERO ATX LGA1150 Motherboard ($199.99 @ NCIX US)
Memory: G.Skill Ripjaws X Series 8GB (2 x 4GB) DDR3-1600 Memory ($79.98 @ OutletPC)
Storage: Samsung 840 EVO 120GB 2.5" Solid State Drive ($84.99 @ Amazon)
Storage: Seagate Barracuda 1TB 3.5" 7200RPM Internal Hard Drive ($53.98 @ OutletPC)
Video Card: Sapphire Radeon R9 290X 4GB Vapor-X Video Card ($579.99 @ Newegg)
Case: NZXT Phantom 530 (Black) ATX Full Tower Case ($119.99 @ Micro Center)
Power Supply: Antec HCG M 750W 80+ Bronze Certified Semi-Modular ATX Power Supply ($79.99 @ Newegg)
Optical Drive: Asus DRW-24B1ST/BLK/B/AS DVD/CD Writer ($19.98 @ OutletPC)
Operating System: Microsoft Windows 7 Home Premium SP1 (OEM) (64-bit) ($84.98 @ OutletPC)
Monitor: Asus VS247H-P 23.6" Monitor ($134.99 @ Newegg)
Case Fan: Apevia CF12SL-UGN 63.9 CFM 120mm Fan ($7.79 @ Newegg)
Case Fan: Apevia CF12SL-UGN 63.9 CFM 120mm Fan ($7.79 @ Newegg)
Case Fan: Apevia CF12SL-UGN 63.9 CFM 120mm Fan ($7.79 @ Newegg)
Keyboard: Razer Blackwidow Ultimate 2014 Wired Gaming Keyboard ($109.99 @ NCIX US)
Mouse: Razer Razer Naga 2014 Wired Laser Mouse ($59.99 @ Amazon)
Total: $1887.18
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2014-08-26 07:35 EDT-0400

If I was to build one to fit your needs this is what it will look like. And just add $200 for monitor and peripheral.
PCPartPicker part list / Price breakdown by merchant

CPU: Intel Core i7-4790K 4.0GHz Quad-Core Processor ($339.99 @ Newegg)
CPU Cooler: Cooler Master Hyper 212 EVO 82.9 CFM Sleeve Bearing CPU Cooler ($29.98 @ OutletPC)
Motherboard: Gigabyte GA-Z97X-SLI ATX LGA1150 Motherboard ($113.99 @ Newegg)
Memory: G.Skill Ripjaws X Series 16GB (2 x 8GB) DDR3-1866 Memory ($166.99 @ Newegg)
Storage: Samsung 840 EVO 120GB 2.5" Solid State Drive ($84.99 @ Amazon)
Storage: Seagate Barracuda 2TB 3.5" 7200RPM Internal Hard Drive ($84.99 @ Newegg)
Video Card: MSI GeForce GTX 780 3GB TWIN FROZR Video Card ($477.98 @ SuperBiiz)
Case: Corsair 200R ATX Mid Tower Case ($54.99 @ NCIX US)
Power Supply: Thermaltake SMART 750W 80+ Bronze Certified ATX Power Supply ($63.95 @ Amazon)
Optical Drive: Samsung SH-224DB/BEBE DVD/CD Writer ($15.98 @ OutletPC)
Total: $1423.83
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2014-08-26 07:36 EDT-0400
 
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