What Gauge of Wire...?

Hi, I would like to know what Gage of wire do I need for my Speakers. Here is what I have.

Pioneer Elite 92TXH Receiver with 130 Watts Each CH.
NHT 2.5i Front Speakers rated at 50-200 Watts (Bi- Wired), Bi-Amped).
NHT SuperOnes for surrounds.
NHT Audio Center One.
NHT Two subwoofers each rated 200 Watts (SW2)
NHT SA-3 Mono Sub Amp rated 260 Watts driving two subs at ones.
Currently I am using regular Speaker Wire from Home Depot. They are 14 Gage. I am on the Budget and can not afford expensive professional grade cables. What is my choice in this case?
Thanks to All