Corsair is a strong choice, as is your CPU. Keep in mind 2500K is for overclocking, 3450 isn't. vmem's comment about a 750 watt PSU to allow a second card in future is a good one, though it means you'd be drawing more power than you need in the meantime.
PSU's don't draw more from the wall than they need (so don't worry - you won't be pulling a constant 750 watts), however they do lose efficiency when they're under-utilised. If total wattage is fairly closely-matched to your actual hardware needs (what's called "full load"), less power is wasted in conversion.
Other side to that argument is that if you do then decide to Crossfire after buying a 500 watt unit and can't sell the 500 when you buy the 750 you need, more money is wasted than the added electricity costs if you just got the 750 in the first place. To be honest, it's not the end of the world either way though - important thing is to have enough power (obviously) and get a quality brand that won't die and/or damage components.
Be aware Corsair and Antec, though frequently recommended, don't actually build PSUs. That doesn't matter (most PSU brands are not manufacturers) as long as they are supplied by OEMs (actual manufacturers) that are quality. Of the OEMs, Seasonic are the widely regarded as the best. Seasonic-built PSUs include all XFX, Silverpower SP-Sxxx / SP-SxxxM / SP-SS lines, PC Power & Cooling Silencer series and Silencer Mk III series. Plus obviously any Seasonic brand model.
EDIT: And that TX650 you mentioned by the way is a CWT-built unit. CWT have been known to manufacturer some quality PSUs, but also some pretty bad ones. Useful resources:
http://www.realhardtechx.com/index_archivos/Page673.htm
http://www.tomshardware.co.uk/power-supply-oem-manufacturer,review-32187-4.html