best way to convert and transfer USD

I am getting ready to send approximately €20,000 EUR to the US. What is the best way to convert the dollars and wire transfer? Would banks such as Ulster Bank and Anglo Irish be the best or a currency broker? I believe Ulster Bank only charges .51 EUR to wire to the US, but the currency rate is about 2 - 2.5 cent lower than FOREX. If a currency broker is used, how much does the wire itself usually cost (noting the conversion rates are much better)?

Thanks in advance.

Exchange rates change up to 1800 times a day. High street banks generally only provide indicative rates and claim that they cannot give you a rate over the phone as it changes all the time. Call into a branch and they will probably tell you that the rate is fixed that morning. A currency broker or a commercial bank would give you the best deal but shop around and see for yourself.