Is it best just to put a mic in front of amp to record or is there a D.I kind of setup I should use. I record into an an analogue mixer then thru a sapphire pro audio interface into Ableton Live on my PC
put a mic in front of an amp speaker. A shure sm 57 works well.
In my opinion that yields the best result if you are getting a good sound out of the amp. You have to be in an environment where you can crank the amp volume up. If you can't really do that direct recording can work well too.
As a general rule mic/amp is the preferred method. Sort of depends on having an amp worth miking, and a mic worth amping, so to speak. What do you have, gear wise?
Why do you have the analog mixer in the sound chain? If you are getting a sound you like from the amp, and mic it correctly, that is exactly what you want to be recorded.