hmmmmm... I have OCZ modstream's, one in each of my comps, one 420w and one 520w (at least I think it's a 520). but anyway, Powmax for me hasnt been very reliable, i've used two of the 400watt demons before and they burnt out within a week of getting them...... but OCZ Pwns.
also check the rating on your current PSU, you may have enough watts, but maybe your PSU is unstable, and the Rails are changing (Basically power currents in PSU) but there should be a sticker on the PSU, it should give it's information, look for a thing that Say's +12v. immediatley after the +12v thing you should see a comma then a number with an A on it, so it should look like this. (+12v, @21A) 21A is just an example.... but anyway, most good PSU's should have at LEAST a 19A rating (in my opinion). also some brands just plain stink with PSu's. like powmax for example. it may have A high +12v Line rating, but it's a lousy PSU maker (some of their casses are nice though).