Antecs are not the best nowadays. They were several years ago but the quality died back. They have since picked up the pieces and started making decent ones again, but my experiences with them in the past make me look elsewhere.
OCZ is a good brand depending on the model. My wife's E6600 system has a 500w stealthXstream, and it is NOT a beefy unit. It feels like one of those rosewill PSUs or something, light duty transformer and smallish heatsinks. I do not like the way that feels, but it has been stable on a non-overclocked rig, so whatever.
One thing to consider though, is if you are not an overclocker or if this rig is used for work/livelihood (hence no overclocking there either) then a 600w OCZ would probably last you a good while even at 100% CPU usage over time. It just wouldn't last
me a good while because Q6600s are power hungry beasts, especially OCed.
If you do go with the OCZ, then you will easily be ready for a dual-core intel in the future. FYI newegg has a rebate on the OCZ model you want:
Newegg.com - OCZ GameXStream OCZ600GXSSLI 600W ATX12V Power Supply 100 - 240 V CB/CE/CSA/UL/FCC - Power Supplies
more up front, but 80 after the rebate.