Really depends what you mean by "high assurance."
Namecheap is just a reseller, and the RapidSSL is the lowest rung of their offerings, so the certificate will say something like "Verified by GeoTrust" on mouseover, but if clicked, will add "organization unknown," or some such, depending on the browser.
Any certificate that actually provides verification of the organization, will cost probably at least $100 or so. Otherwise, it's just domain vaildation, which means that the domain has a working email address and the person who bought the cert has access to it.
It just depends on your business. If you anticipate a large volume of transactions with relatively little customer interaction, then the payment page (and the cert) just became a much bigger part of the credibility of your site. On the other hand, if you have a lot of information about your products, and/or a lot of interaction with customers, then that becomes a major source of old-fashioned assurance.