Hello!
I see you have already gotten quite a few responses here, and so I am going to make a pitch for Worldwide101, which is the virtual assistant company I founded back in 2009. Our team is US based, and we provide "business grade" virtual assistants - so in essence "more than basic admin" and "high quality", which seems to be what you are after. Here is a link to our website http://worldwide101.com/

If you are interested, I would love to find out a bit more about your requirements so we can suggest a VA for you. You can also check out objective VA company reviews on this site http://www.virtualassistantassistant.com/

All the best,

Sandra