Spending $4k in US-cash,credit card or debit card?

Going to USA in a few months,going to buy girlfriend a ring.Probably going to cost between $3 and $4000.Would I be best bring that in dollars and pay commission or just put it on credit card.I've Permanent TSB Ice credit card and Visa debit,dont know which would be better to use.By the time I pay currency conversion fee,would it be more than paying commission?I know paying by card would be safer.Should I let bank know beforehand so they wont be suspicious about such a big transaction?Thanks

Can't speak for the permanent TSB ICE card, is it a Visa or mastercard? Personally I use a credit card for such purchases to avail of insurance and protection.

Its a Visa credit card.Just got debit card on friday,reading here it says debit card transactions outside eurozone will be charged at 1.75% of euro value of transaction(min €3.17,max €11.43).I presume I would get charged max €11.43?Is there an extra conversion fee then applied?

I would have said that €11 is a reasonable fee to pay for the security and ease of using your CC for such a big and important purchase.

The only other way that the cost will be different is if the exchange rate used by the bank to convert the transaction is worse than the retail exchange rate used when you get the cash. Both contain a margin for profit by the bank. I dont know which is worse. If you really want to check, I'm sure you could check this, but asking Permo CCdepartment what rate they are using and compare against the retail rate. I suspect that the difference will be minimal.

True,I'll prob use debit or credit card,dont think theres much of a difference between them.I'm sure if I get 4k worth of dollars I'll be charged more than €11 commission.