Im looking to build a computer and wondering if i can re-use my PSU

I don't think so.
The graphics card is the largest power draw. A 7790 wants 500w and a 6 pin pcie connector.
http://www.amd.com/us/products/desktop/graphics/7000/7790/Pages/radeon-7790.aspx#/2
Your psu does not come close. It also looks like a cheap unit which I would replace regardless.
Stick with a known good quality brand like seasonic, antec, corsair, xfx, pc p&c.....

This corsair 500w unit should do:
http://www.memoryexpress.com/Products/MX41858

Anthony, that is a good choice for a power supply, the reason i suggested 600 watts is for the extra hard drive, fans that are installed, future upgrades, if you have to it's better to spend the $10-$15 now instead of putting more cash later when another upgrade is done. I am running way less then you and I run 600 watt, only because I will be changing, CPU/motherboard and GPU, no need to change PSU again to have sufficient power later. Think to the future and possible changes. Won't be fun to pop out extra $50+ because PSU isn't strong enough again. http://www.memoryexpress.com/Products/MX22557 that"s what I have, works great, already had 2+ years, no problems with it.

Product Info
This HD 7790 Has Factory Overclocking,
System Requirements
PC with:
Windows 8, 7, Vista or XP (Windows XP only supports 2 Eyefinity displays.)
500W Power Supply2 with 1 x 6-pin (75 Watt) PCI Express power connector

here is why, your PSU only gives out 16A on the 12volt rail for the Video at most and your max steady load over time is 380W but has a peak rating of 400W for short periods.

pushing your PSU at MAX amps on the video and high watts (for over all system useage) for long periods of time will require a psu rated for 80-95% (basically what is now bronze silver and gold certified)

here is what AMD.com has to say on the HD7790
http://
500W (or greater) power supply with one 75W 6-pin PCI Express power connector recommended
600W power supply (or greater) with two 75W 6-pin PCI Express power connectors recommended for AMD CrossFire™ technology in dual mode.
NOTE: Minimum recommended system power supply wattage is based on the specific graphics card and the typical power requirements of other system components. Your system may require more or less power. OEM and other pre-assembled PCs may have different power requirements.

85W average power draw for your video card based on another review site basically confirming what toms has: http://

newegg user review: At full load, the card was only using 85 watts & I was able to overclock it stable +150 core, w/o going above 65oC (in ~76oF, 24.5oC ambient).

also something to note, users with unlisted spec are reporting crashing of these cards across the whole vendor spectrum, but not listing system spec or crash problem/analysis

your video card will need a 18 amps at the least i believe, however i think that would be the average high, and i have not done the actual math yet, just going off the past experience estimate in my head. psu should work temporarily until you get a new one if you have a demanding game that you want to play at demanding specs. i would not run it at high spec for very long with out replacing it for something that supplies min 18 amps but preferably 28-36 amps running 460 watts or greater if you're going to game or do graphic arts or CAD with this system on a screen larger than 23". other wise you should for the most part be ok, not fine, but passable for awhile.

No, thermaltake quality can be iffy.
Here is one list of quality:
http://www.eggxpert.com/forums/thread/323050.aspx

you listed mobo but not cpu, but I was looking to go with a i5 3570k, Asus mobo (great quality board BTW) and the same GPU, so I say it's a good build for gaming, but spend $20 more for this http://www.memoryexpress.com/Products/MX44000, better over all and with rebate same price what you chose, everything else good