Brand is important and then the rating on the 12v rail the total power is irrelevant when concerned with graphics cards.
Any half decent power supply though will be more than enough for a 4830 with an overclocked E8400 peak power is ~210W for the system so as long as the PSU has 16A on the 12v rail it will be more than enough.
In comparison the same system with a 4670 draws ~165W, a 9600GT ~180W and a 8800GT/9800GT ~190W (similar performance to 4830).
At a resolution of 1280*1024 (so slightly higher than your TV) using the 4830 as a base line, you lose 12% performance going for a 9600GT and 36% going for a 4670, the 8600 GTS (so better than what you had) is only 46% of the performance of a 4830!
All data taken from Techpowerup review of the Powercolor 4830 (which is the model I linked to before).
Performance -
http://www.techpowerup.com/reviews/P...D_4830/26.html
Power Consumption -
http://www.techpowerup.com/reviews/P...D_4830/24.html