how to run a 230 volt line from my panel??

With regards to the breaker; Yes, a 20A/230V breaker will provide you with the two phases & terminals needed for your run. I'm assuming that 12AWG wire is a dedicated run for your 230V circuit. Wait until you receive the component, find out what configuration the plug is(depends on the country) and get an outlet to match. The option would be to obtain a NEMA 6-20(20A/230V) plug and outlet, then install the plug on the unit's cord. You DO NOT want to run 230V to NEMA 120V outlets. At some point- someone may plug an appliance or component into it, and toast it, or get shocked by the(then hot)chassis.

It's unlikely that your new unit, will have an IEC connector(inlet on chassis) that matches the one on your present power cord(http://www.internationalconfig.com/icc5.asp?productgroup=%27IEC%2060309%20%28309%29%20Wiring%20Devices%20and%20Cord%20Sets%27). If it does; you can use(NEC notwithstanding) what ever plug you choose(IF the cord is rated for 20A). Wait until you receive the component and better know what your are dealing with.

BTW: the site I listed shows the configurations of IEC plugs, 125V(C-14) vs 230/250V(C-20). Note that the contacts of your expected 230V component's connector(chassis end) will be(most likely) horizontal, the ones on your 125V cord are vertical. Of course; you can change the IEC outlet, on your chassis or the IEC female, on your cord(http://www.vhaudio.com/connectors-ac.html#OyaideIEC).