What power supply does he have?
How small are we talking here? As Kennah recommends, the Fractal Node series of cases are quite nice. Here's an example parts list:
PCPartPicker part list / Price breakdown by merchant
CPU: Intel Core i5-6600K 3.5GHz Quad-Core Processor ($273.98 @ Newegg)
CPU Cooler: Cooler Master Hyper 212 EVO 82.9 CFM Sleeve Bearing CPU Cooler ($19.99 @ Newegg)
Motherboard: Gigabyte GA-Z170N-Gaming 5 Mini ITX LGA1151 Motherboard ($124.99)
Memory: Patriot Viper 4 16GB (2 x 8GB) DDR4-3000 Memory ($89.99 @ Newegg)
Storage: Samsung 850 EVO-Series 500GB 2.5" Solid State Drive ($147.99 @ Newegg)
Storage: Western Digital Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive ($49.98 @ OutletPC)
Video Card: Asus GeForce GTX 980 Ti 6GB Video Card ($629.99 @ SuperBiiz)
Case: Fractal Design Node 304 Mini ITX Tower Case ($68.99 @ SuperBiiz)
Power Supply: Cooler Master 750W 80+ Bronze Certified Semi-Modular ATX Power Supply ($74.99 @ NCIX US)
Operating System: Microsoft Windows 10 Home OEM (64-bit) ($89.88 @ OutletPC)
Total: $1545.77
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2015-12-07 16:22 EST-0500
Newegg has the motherboard for $125 after $10 rebate, not sure why PCPartPicker took Newegg off of that item's price listings.
If you absolutely need to fit the parts list under $1500, then consider going with 1x8GB of RAM for now or a smaller SSD.
It's possible to go even smaller, but it'll be somewhat difficult, at least for a first time build.
WOAH I like this alot
you sir have made making a neogaf account worth it