Newegg.com normally doesn't accept payment from multiple credit or debit cards. You can get around this limitation and split your Newegg purchase with a simple trick using this Gift Card.
Purchase a Newegg Gift Card with one of your debit or credit cards. Enter your email address and choose an amount for your gift card that is about half the cost of the item you want to buy from Newegg. Do NOT change the delivery date.
You can purchase a gift card with your custom amount here: https://secure.newegg.com/GiftCard/EntryScreen.aspx
Important: You need to use the gift card I link to because it is the only one delivered by e-mail.
After purchasing the gift card you will be emailed a gift card with a card number and security code. Copy those numbers as you will need use it in the next step.
Now that you have your gift card number you can now proceed to purchase the item you originally wanted to purchase with the gift card and your other debit or credit card.
If you have any questions ask below in the comments and i'll try to answer them.