Do you have a gateway that you are going to use to make payments?
The reason I ask is because I don't know of any way to make payments using an HSBC account. I don't even think that you can use Best Buy credit cards (which are actually HSBC credit accounts) outside of a Best Buy store.
If you just want to do online payment processing, I recommend using ECHO. They have the ability to accept credit card payments using Visa, MasterCard, American Express, Discover, Diners Club, Carte Blanch, and JCB. Their payment gateway also accepts online check payments.
I have used ECHO on a number of sites and haven't had any complaints. The best thing about their software and service is that their payment gateway is completely free to use. Another excellent feature of the service is that you don't pay any monthly fees if you didn't take any transactions that month.
Is this what you are looking for? If not, you really need to be more specific.