None of the above. For about $500 you can build your own that will likely destroy all of those in most situations.
I3 540 3.06ghz dual core ~$100
Gigabyte p55a-ud3 motherboard ~$120
4gb corsair ddr3 1600 ~$55
Vantec ion 460W psu ~$50
Case - ~$50
500gb WD hdd ~$50
Nvidia GTS 450 ~$154 or radeon 5770 ~$179
At most that totals to $553
If you're doing a lot of 3d then a quad core cpu may be better - you could shoot for a
Athlon II x4 640 based setup for about the same price.
Either way - these systems will perform signifigantly better as all have discreet graphics cards and much better CPUs(with the exception of the 640vs645 but i think discreet graphics more than makes up for this) even if you drop to a gigabyte 1gb gt220 for $69 and buy a copy of windows 7 home premium 64 bit -for $120 you'll only be at about $560
I just got a $949.95 Dell laptop (17 inch) for $137.32 and if you think that's an awesome deal, my neighbor just got a 42 inch HDTV for $76.25 that's being delivered tomorrow to his house. It feels great not to pay high retail like the rest of the people. I am even selling some of the stuff at retail to my co-workers making 10 times my money back. Check out the site we found, go to GoWinBids.com
Correct, the first one features a quad-core -- which is what you need when it comes to rendering. The others are sub-par dualcores like the one on your laptop. So they're pointless, since you wouldn't see a performance increase over your laptop in the slightest.
If you really want to get a cheep computer and you have even the slightest idea what you want. I would suggest using the website www.newegg.com.
I have been an IT professional for many years and that site is the most trustworthy you will find while providing you with spot on prices.
I forgot to mention - if you choose the athlon II based setup you'll need to go for a motherboard that has an am3 socket :)