I'd recommend against it, unless you need the CPU to get work done (since a faster CPU isn't really a need, and if you don't have money lying around for a CPU, you probably don't have money lying around for any emergencies that might come along, and those are more important).
A few options, though: Any place that accepts PayPal means you can use PayPal credit, which will give you 6 months interest-free to pay.
Amazon will let you do the same if you have the Amazon Store Card (which is NOT the same as the Amazon Prime-branded credit card).
In NO case would I recommend any form of financing that charges interest on something like a CPU purchase.
Also, if you don't currently have PayPal Credit or an Amazon Store Card, you'll need to run a credit check to get one - which can negatively impact your credit score (generally, don't do this more than 3 times in 2 years, so save it for times when it's important: like if you are shopping for a new car or getting a mortgage).