Autotask is one of the most popular and established PSA vendors with overwhelmingly positive reviews. Autotask prices aren't publicly listed, which usually means that software isn't cheap and sales people may contact you with sales pitches repeatedly. Autotask comes with a wide variety of project management and professional services automation tools, but it appears that it's 100% cloud-based and a self-hosted edition is not available. If you are looking for a free Autotask alternative, the one available both as cloud and on-premise software, with over 35 business tools, consider Bitrix24.
* Please note that the information may have changed since the publication. For current prices and features please visit Bitrix24 pricing page.