Wouldnt paypal automatically take the $150 out of your credit card account when you bought the item anyways?
The way its always worked for me with my paypal account is say i have $20, but the thing im buying is $45.
Paypal would "cover" for the $45 (in that it would tell the company, in this case newegg, that $45 was payed via paypal) and then paypal would deduct the $20 from my actual paypal account, then withdraw the other $25 from my credit card, thereby covering the total $45 that was owed to newegg.
This is all assuming you have a verified credit card on file with your paypal account
(and this all happens automatically when you purchase the item, thats how easy it is)