First, let's take a look at the official ATI recommended power requirementsfor the HD 4830 video card:
450 Watt or greater power supply with one 75 Watt 6-pin PCI Express® power connector recommended
550 Watt or greater power supply with two 75 watt, 6 pin PCI Express® power connectors for ATI CrossFireX™ technology in dual mode
The recommendation is for an entire pc system.
Next let's take a look at actual power consumption of the video card:http://www.techpowerup.com/reviews/Inno3D/GeForce_210/28.html
A system with two HD 4830 video cards does not require very much power.
An appropriate choice would be the Corsair VX 550 power supply. Corsair has a reputation for high quality power supplies. They consistently earn high marks in technical reviews. They are very stable, reliable, and come with a generous warranty.
You mentioned the Corsair TX650 power supply. It is another high quality power supply that would provide you with a future upgrade path. You would be able to upgrade to the HD Radeon 5000 series video cards. If it is available for a good price, then go ahead and buy it.