Like any business, it's a zero sum game.... the better price you get for what you spend, they less money they make. If you have no other resources, i would formulate a relationship with a local MoM and Pop computer place and give them a parts list and have them build it for you. Local computer clubs, High school clubs will often do this, many will sit there and help while you do it.
I'll come up with a suggested build for you. I'll use 7600k as the base build since 7700k brings a bit but not much to the table.
Air Cooled Build
PCPartPicker part list /
Price breakdown by merchant
CPU: Intel Core i5-7600K 3.8GHz Quad-Core Processor ($234.89 @ SuperBiiz)
Again, not the top dog but it's $90 cheaper and ya don't give up much at all, especially if OCing
CPU Cooler: Phanteks PH-TC14PE 78.1 CFM CPU Cooler ($74.99 @ Amazon) Not the best air cooler but the best is just too fugly ... this one looks good
Motherboard: MSI Z270 SLI PLUS ATX LGA1151 Motherboard ($132.35 @ OutletPC)
Considered a moderately proced board but gives ya all you need.... unless a wild overclocker, you don't need anything more.
Memory: Corsair Vengeance LPX 16GB (2 x 8GB) DDR4-3000 Memory ($119.79 @ OutletPC)
Storage: Plextor M8Pe 256GB M.2-2280 Solid State Drive ($129.99 @ Newegg)
Decent SSD w/ cooler
Storage: Seagate FireCuda 2TB 3.5" 7200RPM Hybrid Internal Hard Drive ($99.99 @ Amazon)
Outperforms anything else in its size range by 50%
Video Card: MSI GeForce GTX 1080 8GB DUKE OC Video Card ($534.98 @ Newegg)
Place holder for 10780 Ti
Case: Phanteks Enthoo Evolv ATX Glass ATX Mid Tower Case ($179.99 @ Amazon)
Superb features and performance combined with aesthetics worthy of an art museum
Power Supply: EVGA SuperNOVA G2 650W 80+ Gold Certified Fully-Modular ATX Power Supply ($88.89 @ OutletPC) There are better, but excellent PSU and decent price.
Operating System: Microsoft Windows 10 Home OEM 64-bit ($88.58 @ OutletPC)
Monitor: Acer XB271HU bmiprz 27.0" 2560x1440 165Hz Monitor ($719.99 @ NCIX US)
You didn't say whether monitor was in budget but this is **the** best gaming experience offered today ... at least until 4k IPS @ 144 Hz arrives next quarter.
Total: $2404.43
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2017-03-31 13:16 EDT-0400
1. Obviously, the 1080 Ti will replace the 1080 and will add about $175
2. Again, 7700k doesn't bring much to the table but if ya have the extra $100, why not
3. If ya into overclocking big time, can look at something like this:
http://pcpartpicker.com/product/M9X2FT/msi-z270-xpower-gaming-titanium-atx-lga1151-motherboard-z270-xpower-gaming-titanium
4. If ya like the idea of water cooling, just skip all the CLC types and grab the Swiftech H240 X2... its a collection of real custom loop components preassembled at factory and it outperforms every CLC on the market while being half as loud.
http://www.swiftech.com/h240x2.aspx
5. The above allows you to expand the loop and add a water cooled GFX card. The Ti version of this will be arriving shortly. Add a few inches of tubing and 2 fittings and ya good to go.
https://www.newegg.com/Product/Product.aspx?Item=9SIA1N84RY6499