LOL @ BEST BUY, no offence, but do not purchase anything there, they are junk. ok here is exactly what you can do, and its middle range priced and VERY EXCELLENT computer components.
go to the sony store and buy a desktop computer RB series (probably 3 ghz cpu dual core pentium D processor with 1 gb ddr2 ram) ddr2 is faster than ddr and only intel boards support it. NOW, this is a pci-e board, so you can go and buy the nvidia geforce 7800 gt 256mb pci-e graphics card which is WICKED AWESOME. it can run the top graphical games today like FEAR on max settings (but only 1024x768 res for FEAR)
ok so now you have a computer and graphics card, next thing is probably power supply, since the card takes a lot of juice. get the Antec 550watt power supply, its affordable and very well worth it. Now you're running a monster machine

if you feel like it, add a floppy drive, get a new case for it, mod it, whatever. and the computer has a 7.1 surround sound card integrated.
almost forgot to mention, this will only cost you around $1700 american... thats for the computer, the graphics card, power supply, new fancy case (if you want). the computer comes with keyboard, mouse and speakers, but not a monitor... i personally dont like sony monitors, ive had bad experience with them, so i would suggest an LG monitor or BenQ. (and just because a company makes good computers, doesnt mean they make good laptops, monitors etc...)
also a good GAMING keyboard is the logitech G15, all the keys are backlite blue, it has LCD screen telling you cpu usage and ram usage, and it tells you the date and time and calendar, and it has 18 programmable G keys for macro with 3 different functions for each key, so 18x3 programmable keys. it also has multimedia functions for sound and media players built onto it. and it has 2 usb ports build onto the motherboard to link devices. and a good gaming mouse would be logitech G7 cordless mouse. it comes with 2 lithium ion rechargable batteries with a charger, and the charger has a usb port on it for devices. the mouse has 10 programmable buttons on it and can change anywhere from 400 - 2000 dpi with the press of a button, you can program it to be whichever dpi you want. very good gaming mouse because it has the extra buttons on it so you dont have to use keyboard as much. has super sliding gaming feet on the mouse so it has consistant smooth motion, and it has a low battery warning so you can change the battery. what i do is i have one battery charging all the time and the other in the mouse, so when my mouse is dying i just change it in like 5 seconds.
so the keyboard is $100 usd and the mouse is another $100 usd... all together for everything your lookin at probably $2200 - 2300 usd... insane equippment.