I've been in the market for a new PSU and just saw that Newegg has the 850 Watt Thermaltake ToughPower (PS-TPD-0850MPCGUS-1) for:

$99.99
- $20 w/ promo code TT882015
- $30 rebate
= $49.99.

Shipping is Free.

I can't imagine you'll find a better $50 PSU any time soon.