Best application monitoring system with dashboard

I have been playing with Graphite as application monitoring system but I'm wondering if there's something better out there for what I want.

Here are a few requirements I have in mind:

• Dashboards (easy to create/change)
• the items on the dashboard should be mostly charts but also colored "number boxes" (a la http://shopify.github.io/dashing/)
• when a metrics goes below/beyond a certain value show some warnings on the screen (different frame/background) and potentially send an email
• setting up a rule-to-warn (see above) should be simple to do and have many ways to specify a threshold (absolute value, +/- the min/max/avg over the past 30 days, percentile, etc...)

I would prefer open-source but I'm open to commercial products especially cloud-based solutions.

Any suggestions?

Many thanks in advance.