Are Any of These Good Gaming PCs?

I really only ever play Minecraft, Left 4 Dead 2, Planetside 2, and TERA. I've been doing so on a laptop so far, but (other than Minecraft packs under 200 mods) those games are pretty CPU intensive and tend to overheat my laptop rather quickly, even with my cooling pad, or drain my battery too quickly. I've decided on a max price of 500 dollars including upgrades, since my friend is willing to sell me his gaming desktop for that much (32gbram, 6core RFX290 FAT2 chip set, 6 fan cooling system, 500gb hard drive, 280 watt power supply).
I like these for the prices, especially the Lazer, but I would be buying 8+ gb RAM the moment I get it. Are any of these good gaming PCs, just for what I'm playing? And are any of these companies really reliable? Most of the bad reviews are responded to and corrected, but the ones that aren't are absolutely unacceptable, like broken parts or having no OS.
http://www.amazon.com/...PDKIKX0DER
http://www.amazon.com/...00D1KX2M4/
http://www.tigerdirect.com/applications/SearchTools/item-details.asp?EdpNo=4959030&Sku=C477-G1411
http://www.newegg.com/...6883229285" class='ext_link'>http://www.newegg.com/...6883229285

Added (1). New Egg url:
http://www.newegg.com/Product/Product.aspx?Item=N82E16883229285&nm_mc=KNC-GoogleAdwords-PC&cm_mmc=KNC-GoogleAdwords-PC-_-pla-_-Desktop+Computers-_-N82E16883229285

I think so

Last one yes, it at least has a low-mid range dedicated video card and a 500W PSU. That is the prime thing to look for if buying any gaming computer, the video card. Nothing in it however, screams of "great machine", but at least you can do some minor upgrades in a year or two.
All the others (Amazon) seem to have integrated video (APU/GPU) - video built into the processor. One (Tiger) had a lower end GT720 video card - the R7 240 is better.

Your "friend" trying to call a system with only a 280W PSU a gaming machine, is stretching the truth a lot there… A 280W PSU can't run any reasonable video card, not enough power.