Looking at upgrading code can anyone recommend a good version to move to for the ASR currently on the below version
cisco ASR1001 (1RU) processor with 1207128K/6147K bytes of memory.
4 Gigabit Ethernet interfaces
32768K bytes of non-volatile configuration memory.
4194304K bytes of physical memory.
7741439K bytes of eUSB flash at bootflash:.
For ASR1001 3.16.8S looks to be recommended version.
Please check related code documentation and hardware requirements before proceeding with any IOS upgrade.
No, you can go direct, however, read the Release Notes carefully.
Just make sure you take the opportunity to upgrade the ROMmon/Bootstrap.
In general, with in the same major train (3.x), you can go directly. However, as Leo suggested please read the release notes and chances are that you may have to upgrade ROMMON. Make sure you take backp of the configuration and existing code from the device and schedule a maintenance window. If you got SMARTnet support, open a pro-active ticket.