NVIDIA GEFORCE GT 610 1GB sucks whats the best upgrade for under 400.

PCPartPicker part list / Price breakdown by merchant / Benchmarks

Video Card: Asus GeForce GTX 770 2GB Video Card ($348.99 @ Amazon)
Total: $348.99
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2013-12-25 12:29 EST-0500)

GTX 770 will require a 6 pin and a 8 pin power connector from PSU, so just make sure that PSU has it. Actually OEM PSU's are cheaply made, and they over-rated their wattage than actual. If you need a PSU in any case, then you can have this :

PCPartPicker part list / Price breakdown by merchant / Benchmarks

Power Supply: XFX 650W 80+ Bronze Certified Semi-Modular ATX Power Supply ($82.99 @ NCIX US)
Total: $82.99
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2013-12-25 12:37 EST-0500)