Upgrading the breaker to 20 AMP just means you are going to start a fire quicker.  The wiring is probably not the correct size for 20amp.  The only way to safely upgrade is to upgrade the breaker and the cable.  I'd highly suggest having an electrician run a new line that 240V 30AMP and use that as you can get several rigs on one line that way.

Previous guy mentioned it, surge protectors are by jules not watts/amps.  Most surge protectors have a max draw (usually 1200w or so).   Plug 1 PSU into 1 surge and the other into another surge and run a good extension cord to another line in another room that's not on the same circuit.  That's the safest way you are going to be able to run it in your situation without running new lines/breakers. 

I'd do this soon, you are asking for a fire on a 15amp line.  It could be slowly burning away/melting in the wall and you won't know it until it's too late.