You will get the lowest rates using this as long as your current processor has you set up properly. Also easily integrates with QuickBooks and even enhances QB performance.
For Level 3 processing I highly recommend PayTrace which is a phenomenal gateway that automatically defaults all your transactions to Level III and that would save you money on all your downgraded transactions such as EIRF and Standard and provide you great savings. Cards that will also go through at reduced rates are below and also attached. Also their customer service is unparalleled in the payment gateway industry.
Visa Purchasing and GSA Purchasing cards 1.80%
MC Purchasing and GSA Purchasing cards 1.80%
MC Fleet cards 1.80%
MC Corporate cards 1.80%
MC Business cards 1.80%
MC Business Enhanced Value cards 1.92%
MC Corporate World cards 1.97%
MC Corporate World Elite cards 2.02%
Visa Signature Preferred, Corporate and Business cards 2.05%-2.10%
The best integration available for Quickbooks if needed is http://verosa.com/
Thanks and let me know if you want more details.