Sysadmin service recommendation for setup & maintenance?

We have a few linodes that we've been using for hosting a small app, and demoing another that we have been working on. I've been handling setup and maintenance, but we are getting ready for a beta and bringing in more users, and I'd like bring both more expertise and manpower to bare.

I'm looking for a service that can set up instances, monitoring, backup, configuration management, etc, for maybe a half dozen servers to start, and help us grow and/or migrate to dedicated machines in the future. I'd also like 24/7 coverage for system availability and 1st tier support for any application issues (slowdowns, failures, etc; not end-user helpdesk stuff). The ideal service could also help with Postgres failover, replication, backup & recovery.

When I say service, what I'm really concerned about is not relying on just one or two people.

I'm imagining that we'd pay an hourly or day rate for initial setup and major upgrades, and then some sort of retainer for the ongoing coverage.

(We use ubuntu, nginx, ruby/rails, postgres, rabbitmq, and a custom service we've written in C/C++)

Thanks.