Here is the list. You friend can buy either SSD or better GPU, and the price will be a little bit over the $800 budget. If your friend does not want to it will be OK.
PCPartPicker part list:
http://pcpartpicker.com/p/2kIdU
Price breakdown by merchant: http://pcpartpicker.com/p/2kIdU/by_merchant/
Benchmarks: http://pcpartpicker.com/p/2kIdU/benchmarks/
CPU: Intel Core i5-4670K 3.4GHz Quad-Core Processor ($222.00 @ Amazon)
CPU Cooler: Cooler Master Hyper 212 EVO 82.9 CFM Sleeve Bearing CPU Cooler ($29.99 @ Microcenter)
Motherboard: MSI Z87-G45 Gaming ATX LGA1150 Motherboard ($99.99 @ Microcenter)
Memory: Crucial Ballistix Sport 8GB (2 x 4GB) DDR3-1600 Memory ($64.99 @ Newegg)
Storage: Seagate Barracuda 1TB 3.5" 7200RPM Internal Hard Drive ($59.98 @ OutletPC)
Video Card: Gigabyte Radeon R9 270X 2GB Video Card ($215.91 @ Newegg)
Case: BitFenix Merc Alpha (Black) ATX Mid Tower Case ($29.99 @ NCIX US)
Power Supply: Antec Neo Eco 620W 80+ Certified ATX Power Supply ($39.99 @ Newegg)
Total: $762.84
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2013-12-15 12:36 EST-0500)
Because the FSX is the cpu intensive game so I choose intel instead of the AMD cpu.
http://www.jetlinesystems.com/performance.php