not sure what the good tower coolers are these days, but keep in mind it has to ship across country assembled. there will be no overclocking.
No matter the cooler choice, you'll need to secure it from moving while being manhandled across the country
-ASUS P8Z77-V LK ATX Intel Motherboard with UEFI BIOS $149.99 (overkill?)
Nice feature set, has Fan Xpert+ so you can preset the profile for him.
-Intel Core i5-3570K 3.4GHz (3.8GHz Turbo) LGA 1155 Quad-Core Desktop Processor $229.99 (seems like a good cost to performance ratio...)
If no OC, then don't need the K.
-SAPPHIRE Radeon HD 7850 100355L Video Card $209.99 (Looks loud! anyone heard one?)
You haven't said his monitor resolution and whether you want the bling on maximum while gaming...Assuming 1920x1080: I've been tracking HD 7850 reviews here
...and GTX 660 Ti reviews here.
I'll let you look at the benchmarks to see which GPU is a better fit...it's a ~$200 or $300 choice. I'm enamored with the MSI Twin Frozr IV solutions for both GPUs. Awesome cooling, decent noise levels.
-G.SKILL Ares Series 8GB (2 x 4GB) 240-Pin DDR3 SDRAM DDR3 1866 (PC3 14900) Desktop Memory $56.99 (is it worth it to get such fast ram?)
Not unless you OC. Otherwise, 1600 1T is fine. The low profile is a good choice.
-Rosewill CHALLENGER Black Gaming Computer Case $49.99 (meh)
My eyes! My eyes! Don't make me drive north and take a sledge to that.
-SAMSUNG 830 Series MZ-7PC128B/WW 2.5" MLC Internal Solid State Drive (SSD) $118.99 (nice!)
-Western Digital Caviar Green WD5000AZRX 500GB $79.99 (yes he only wants 500GB, dont ask me why, I might just stick a red 1TB in and not tell him.)
If you don't have a digital movie collection, then 500GB is fine.
-Rosewill Green Series RG630-S12 630W Continuous @40°C,80 PLUS Certified, Single 12V Rail, Active PFC "Compatible with Core i7,i5"
Power Supply $59.99. the PSU im not sure about (other than i probably being overpowered and most likely loud...) think a seasonic g-360
Your stressed load is in the 250W range with the 7850..add another 20W for the GTX 660 Ti. Hardware Secrets
thought the Rosewill PSU passed muster for meeting specs, but don't know how loud it is. No reviews out yet on the Seasonic G series. The 360W model would be fine, load power-wise...but don't know what the fan profile is like - or if that matters to your bro.