I use several of Uniquetek's gadgets on my 550: Mic. Powder Bars, Hopper baffle, Turbo Bearing, Toolhead clamp Kits. These seem to "tighten the machine" up really well but I'm not really sold on the clamp kits. First let me say that 80% of my loading is for cowboy action and informal paper target shooting. The rest is for accuracy with the 1911 in 45ACP. The stock tool head is plenty stable and tight just as Dillon makes it and I have found that a very little wiggle room is good anyway. When I'm running reasonably fast with 45 ACP, the machine will occasionally hang up on a case top in the decap/prime station when using a tool head with the clamping kit installed...Soooo for my 45ACP's I use a stock tool head. The Mic. Powder Bars are great (!!) and, combined with Uniquetek's turbo bearing on the shell plate, I think my seating and charges are more consistant. I do not use the 2X hopper tube but I do use their powder baffle. The standard Dillon tube holds enough powder to load anything I want in a single session and I believe the baffle might help keep the powder from compressing with a full tube. As far asa the shell plate illuminator...I use a small goose neck lamp mounted to my strong mount behind station 3...If you have a 650 just buy the Dillon Powder Check.
I'm a gadget sort of guy...but, while I think these products work well, I also think Dillon does a great job with their machines just as they are and when It comes down to brass tacks maybe I'd be better off saving the money and buying more powder, primers, bullets and such
That's my story and I'm Stickin to it