why would you consider buying a gt430? please tell me what made this thought come into your head? have you read a review of it? they are sloww and poor value for money. get an ati 5570 ddr5 low profile http://www.tomshardware.com/reviews/geforce-gt-430-gf10.... List the full specs of your pc so we can determine if your psu may blow up, including the PSU's 12v amp rating.
no, you dont want a 5450, you wont be playing games on that card, just watching a slide show.
14a (max) on 12v rail = 168W max on the 12v.
5570 total system under load 175w from the wall http://www.anandtech.com/show/2935/13
so assuming your psu is in good condition and not faulty, you should be ok