Not enough info really. What is the exact model? You can not assume that dual 18 amp rails = 36 amps combined, it could be under 30 amps. The Antec Smartpower 500W has dual 18 amp rails with a max of 25 amp combined. At least one of the Thermaltake 600W PSU's max combined is only 29 amps, which is probably fine though given your system specs. Anyway to be safe you need to get the exact model or better yet see if max combined 12v is given in amps or watts.
I agree with Evil but Pauldh has a valid point. The brand is fine I'm using one myself. The PSU itself should tell you what the combined amps are. You can't assume 18a + 18a = 36a.
Saying that though I'm 99% sure that it will work just fine without any issues.