By only offering Google Checkout is a site losing business?

What are peoples thoughts on this? My site currently only offers google checkout. I'm curious if anyone started with google checkout and later added a checkout system that doesn't require the sign up and won't direct customers off-site to check out...and if this is you, did it increase sales? My site is a one product site that is doing 1-2k a month in sales. One product, so a simple solution will do. I feel now that sales are up and running adding the option of CC checkout on site would increase sales? Anyone? Also what is this simple checkout solution I'm looking for. Thank you!

Aything you do to make it easier and more trustworthy will help.