Some great options there, although if you're going the Seasonic route I'd take the newer S-12 Energy+ or M12 units over the older S12 series.The best bang for the buck right now seems to be the Antec Trio Rail TP-3 650 watt PSU which is really a Seasonic rebadged (seasonic is pure top shelf)
they are around $110.00 or lower on newegg wicked quiet too!
the real horsepower is the Seasonic S-12 600 watt but it will be real close to your budget of $150.00 ?????? thats cadalliac unit
same with Corsair HX 620 (also by seasonic)
Thermal take Tough power 650 watt
all the above are 85% efficient at rated at 50C case temps >>>>> no games for these units; just real power
Some great options there, although if you're going the Seasonic route I'd take the newer S-12 Energy+ or M12 units over the older S12 series.
The Antec TPIII-650 is worth considering as a budget 'bang for the buck' unit.
The Corsair HX620 is a great quality, modular PSU, that would be towards the top of my list.
The Silverstone OP750 will give you an enormous amount of upgrade headroom, but is at the ceiling of your budget.
All of these units are fine for gaming systems. Are you planning on upgrading your system significantly? All of these units are significantly more than is required for the hardware you have now.