Yup, the 2500K - GTX 570 pair can indeed play BF3 and SKYRIM on ultra settings on a 1080p monitor with decent FPS. When it comes to future proofing, your build would be good for several years and I would be the first to be shocked if after 3 years it couldn't even play all games on mid settings because I strongly believe that even though technology (of which gaming is included) is indeed changing rapidly, it is not that fast and there is always a limit of what you can do.
But if you could build it yourself or have a friend assist you, it be best and more worth your money, here is an example of a COMPLETE gaming build that is under $1300:
Intel Core i5-3570K Ivy Bridge 3.4GHz (3.8GHz Turbo) LGA 1155 77W Quad-Core Desktop Processor Intel HD Graphics 4000 BX80637I53570K - $230
ASUS P8Z77-V LK LGA 1155 Intel Z77 HDMI SATA 6Gb/s USB 3.0 ATX Intel Motherboard with UEFI BIOS - $150 ($130 after rebate)
G.SKILL Ripjaws Series 8GB (2 x 4GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) Desktop Memory Model F3-12800CL9D-8GBRL - $46
Seagate Barracuda ST3750525AS 750GB 7200 RPM 32MB Cache SATA 6.0Gb/s 3.5" Internal Hard Drive -Bare Drive - $70
SAPPHIRE Radeon HD 7870 GHz Edition OC 2GB 256-bit GDDR5 PCI Express 3.0 x16 HDCP Ready CrossFireX Support Video Card (11199-03-20G) - $310 ($295 after rebate)
OCZ ModXStream Pro 600W Modular High Performance Power Supply compatible with Intel Sandybridge Core i3 i5 i7 and AMD Phenom - $75 ($50 after rebate)
COOLER MASTER HAF 922 RC-922M-KKN3-GP Black Steel + Plastic and Mesh Bezel ATX Mid Tower Computer Case with USB 3.0 and Black Interior - $90 ($80 after rebate)
LITE-ON 24X DVD Writer Internal 24X DVD+R 8X DVD+RW 24X DVD-R 6X DVD-RW 16X DVD-ROM 48X CD-R 32X CD-RW 48X CD-ROM Model IHAS324 - $22
Rosewill Gaming Keyboard RK-8100 (RIKB-11003) - $25
RAZER Abyssus Mirror Special Edition Black 3 Buttons 1 x Wheel USB Wired 3500 dpi Mouse - $30
inland Home/Office Series 88034 7.2 Watts 2.0 Speaker - $10
Acer S220HQLAbd Black 21.5" 5ms LED Backlight Widescreen LCD Monitor 250 cd/m2 ACM 100,000,000:1 (1000:1) - $120 (1080p)
Microsoft Windows 7 Home Premium SP1 64-bit - OEM - $100
TOTAL : $1278 ($1178 after rebate), this is a complete build that can let you play all games on max settings with good FPS on a 1080p monitor and higher resolutions.
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The HD 7870 is faster overall than a GTX 570, especially that the one I provided is an OC version, and not to mention that it is considerably more power efficient.