Anchoring depends on your bottom and conditions. I also own a 620T and carry several anchor combinations depending on what conditions I'll be fishing. I don't keep them all in the boat for weight and/or space reasons but if I know what conditions I'll be fishing I'll take whatever out of the truck and put it in the boat for the day.
First thing I can tell you from experience is that (2) 28# navy anchors, each with 6' of chain and 120ft of cord, attached to the bow of my 620T will not hold my rig still on a Mille lacs mud flat in 26-28 fow with 3 ft waves... I have found only one anchor which will do so. Note that I have no affiliation with this product as far as a sponsor or other - I just use it because it works... Check the link:
http://www.marinetechproducts.com/page/135. The 9400 water spike is sold as a 22-35ft boat anchor... yet only weighs 16#. If you watch the video at the end of the page you'll see how easy it is to deploy and retrieve. I have found it to work awesome on sand/mud/clay/weedy/and rocky bottoms. It doesn't work so well in hard gravel areas as the tips seem to not grab. My only gripe is that the thing is large and clumsey on the bottom of the boat... It is however light, easy to deploy and retrieve and holds.
catfish