When choosing a shared hosting partner I would suggest to go for our hosting partners, which can be found here:
Still, in 5.1 ( as Markus noted ) you have the option to switch off, modules that you do not wish to use, which can save you a lot of memory, so I guess, you are free to try other hosting providers as well. However we cannot guarantee that Sitefinity will be performing as good as when using a hosting partner's service.
the Telerik team
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