With the amount of money you're dealing with, wire fees won't matter, but the spread is very important. Ideally you want to be able to do a spot trade, so you can trade on a realtime market where the real market rate is changing every second, and you want the spread to be small.
There is only one broker who operates in both the US and Europe, where you can ACH your USD (at no cost), trade the USD for EUR at the right moment (using a limit order if you prefer) with full transparency on the rate, and then wire the euros out of Germany. Interactive Brokers can do that. I have no idea what the cost will be to wire euros from Germany to Ireland; that's what you have to consider. The spread is tight, like ~2 pips, and the transaction cost is $2.50, so the broker doesn't make much on a single trade.
The big downside is the painful signup process and learning curve. It's a ten page form to fill out when opening an account, and several of the answers are non-trivial. Then you have to wait for a security device to come in the mail. There's also a $10 min. monthly activity fee, so if you do one trade, you'll pay $2.50 for the trade, and $7.50 to meet the min.
IB is not generally worth it for one transaction, but if I were moving 6-7 figures as you probably are, it may be worth the hassle. Just about any money transfers company is a ripoff. There's no transparency, and a number of ways these places can hide a big profit. With IB, the only part where you don't have transparency is the wire from germany to ireland, but at least there's no currency difference. It may cost nothing to wire from Germany to Ireland since both are in SEPA - but there's never a guarantee. Some SEPA banks still charge wire fees.