Thanks for the reply, but my computer case is very restrictive. I also forgot to mention that I need a mATX psu. The power supply has to have a fan on the side of the power plug. Also, it can't have an on/off switch on the back. Do you have any more suggestions?
anything around 400W is enough for that build, provided you dont want to upgrade anytime soon.
but for heaven's sake, do NOT buy that PSU, get a Corsair or an Antec, maybe an OCZ or an XFX... just get something certified as more often than not an uncertified PSU can, at best, leave you stranded or, at worst, kill your build, without prior notice.
For a system using a single GeForce GTS 450 graphics card NVIDIA specifies a minimum of a 400 Watt or greater power supply that has a combined +12 Volt continuous current rating of 22 Amps or greater and that has at least one 6-pin PCI Express supplementary power connector.
The HIGH POWER SI-A400M2, that you've linked to, has a combined +12 Volt continuous current rating of 15 Amps (i.e. HIGH POWER states: +12V1 & 12V2 combined output should not exceed 180W) and with one 6-pin PCI Express supplementary power connector, is too under powered for a system using that graphics card.
What is the make and model of your case? If the case is from a consumer desktop unit (e.g. Acer, Compaq, Dell, Gateway, HP, Sony, etc.) then provide its make and model number.
Thanks so much everybody. I just realized that when I take out the power supply, there would be a hole at the back of the PC. I thought the power supply metal was part of the case lol herp derp. One last question, both Geek and Ko888 have presented me with power supplies that have a fan on the top. I can't see a possible way to install that. Could you both enlighten me on how that is possible?