Oh cripes is this another Mac-altar thread?
Save your money. Simple as that. You wanna know how to get the best for your money? Build your own machine. Get stuff that actually matters - like a solid state drive, to help alleviate the #1 bottleneck and cause of worse performance in any and every computer today. Get a 24" monitor so you can actually have a working space bigger than only being able to look at 10% of your image at one time.
Memory and processor speed is probably least important. Fact is, people were running Photoshop on dual-core processors just fine, and Photoshop doesn't take up 8 GB of RAM by far - more like 2 GB at most. Get 4 GB if you want to feel safe. So you'll take 5 mins to crunch something that would otherwise take you 3.5 mins - seriously, decide where your money is best spent.
The best way to spend a limited budget is to 1) save to expand it and 2) build your own machine. You don't need an Intel processor - AMD processors, while not nearly as fast at the high-end, really caught up and dominate the low-end market due to their low cost. You can get a 3-core AMD processor for $115, paired with an $80 mobo, $70 for 4 GB of fast DDR3 1333 RAM, maybe $50 or $60 on a video card, which brings us to.... $325. Add $230 for a SSD to store Photoshop on, $100 for 2 320 GB drives for RAID 1 to a) actually have room for your photos and b) make sure that they survive in case one of the disks crashes, $100 for a cheap case and decent power supply ($30 for a DVD burner if you really can't use the one from your old computer), use the keyboard and mouse, speakers, and printer from your old computer (pirate Windows and Photoshop but shhhhhh on that

) and we're talking about an approximately $700 computer with brand-new components and full (often lifetime) warranties that will absolutely, totally smoke the computer you linked.
Then add $100 for a Wacom Bamboo tablet so that, you know, Photoshop is actually usable, and $300 for a basic 24" display (or just use the monitor you already have... that's OK in a pinch) and for about $1100 you've got a kick-ass machine that'll do pretty much anything you could want and do anything related to Photoshop with kick-ass speed.
Or, you can either a) get a crappy machine that somebody returned (or worse... it is refurbished) with no warranty to save your ass if the hardware is a lemon and tough **** when your hard drive inevitably crashes, b) pay the Apple Tax so you can have the same status-symbol machine that stopped being cool when everyone and their grandmother got their hands on one, with inferior hardware for the price that doesn't even really meet your needs in the first place.
Or you can spend 20 minutes researching on Google and seeing that if you have the dexterity to put together a Lego set, you can put together your own computer in a fool-proof manner over the course of a few hours on the weekend, have fun while doing it, learn something about your computer, and save hundreds of dollars while doing it. Your call.