XERO is a great product - I am really blown away by the functionality. It has a limit in that it doesn't do payroll - or at least the last time I looked so that is the only downfall.
Otherwise it is a great product.
Have a look at
www.saasu.com as well. Whilst not as prettyy as Xero it does a great job. And payroll is pretty easy to deal with.
Good luck.