I lodge dollar cheques to my account every month.
There is very little difference between them. Bank of Ireland don't charge commission but generally tack on an extra 1.5% to the standard ECB exchange rate for that day, which is pretty reasonable.
Was thinking about opening an account with internaxx to get good exchange rates, because they said they do commission free forex, but when I investigated this further they did the same thing as Bank of Ireland. Don't charge any commission but tack on extra percentage to the standard interbank forex rate or something (can't remember what they said but it wasn't the ECB exchange rate, but i'm sure it's something similar).
In conclusion, I'd recommend just lodging it to your own bank account.
And I wouldn't recommend waiting for the dollar to get stronger or weaker against the euro - you just don't know which way it is going to go. But the generally concensus is that the dollar is on a steady slow downard decline with no change in store unless the twin deficits is sorted out, which is very unlikely. So I'd lodge that check to your bank account as soon as you can.
Also it's a very bad idea to leave checks, and not to lodge them. You never know what will happen to the bank account that is being drawn on, and it can take checks 3 weeks to clear if it has to go to a US bank account.
Hope all that helps!