I have used Idera Diagnostic Manager for a log time now. I really like their dashboard where you have a one shot view of all the metrics that you would want to identify any performance issues.

I also use there alert system to get alerts on my email. You can tweak there already made templates for most of the monitoring metrics of a server : like cpu usage, job failed, deadlocks, disk io, disk space, page fragmentation,locks and blocks and lots more. Even reconfigure your own threshold for those metrics [Normal,Informational,Warning,Critical] according to your own preferences.. You even have a choice to create your own metrics.

This alert has greatly relived me from worrying about the server state and not having to babysit the server all the time.

I have not used REDGATE tools , but really want to try it. So I cannot compare between these tools as i have not tested all. I'm just writing here some of the features that may be useful and exactly what you are looking for.

Overall, Idera DM is a tools where Identifying performance related issues is very easy and quick. Further Diagnose and troubleshooting may take some more effort. Dm won't do everything for you.