XFX XXX 650W is a modified SeaSonic S12. It has some issues when given low +12V loads. Not my favorite PSU.
Corsair TX650 is a CWT PSHII. It's decent, a bit above the XFX.
Corsair TX650v2 and the XFX Core 650W are both the same SeaSonic platform, a step up from the others listed.
I looked up the prices here today, and it seems that XFX Core650W is the cheapest of the lot, equivalent to around 134$ (USD) plus taxes. So, according to you I can safely pick this one up rather than the XXX edition. One question though, do you think the benefits offered in the core edition are worth sacrificing the advantages of a modular psu?
Also, which one would you have picked, XFX core or TX650?