DoS attacks are really easy against Tor hidden services. The service can't block the attacker because all clients are anonymous. Tor hidden service introduction points can sometimes also be DoS-attacked. I wouldn't use Tor to run a site like this.
what would you use to run a site like that?
I'd use i2p if Tor was compromised. Setting up i2p is only a little more challenging than downloading Tor tools, since these are usually pre-configured for the user. I2P requires some study to understand how it works and how to use it, and a lot of i2p services are hacked together from different projects, so they take some effort to learn how to use them effectively. This can also make i2p seem significantly more secure, so it seems like a logical place to launch a service similar to SR. Getting vendors to sign on to an eepsite instead of an onion website is the real challenge, but when there is a market niche to fill, smart entrepreneurs will step up to the challenge.