Joe, I'm glad you're considering a bino-viewer. It will suit and compliment your selection of scopes very nicely.
A good used Denk II with OCS, dual arm power switch, and Newtonian extension tube system will run around $650 used and they seem to be readily available, especially if you float a "wanted" ad. I have a couple of them and they are all excellent optically and ergonomically. I see little, if any, optical differences between my Denk II's and my Bino-Tron. The Tron is lighter than the Denk II, has a nice rubber coating, and an easy user collimation adjustment feature. The Tron's optical light path is, however ~ 1/2 inch longer than that of the Denk II. The same Tron/power switch/OCS system will run a good $150 more on the used market and they are less available. I find there is no "bad" choice here, both will bring a lot of pleasure to your viewing.
As you have some SCT's, I strongly recommend getting a Baader T2 prism diagonal, or the more expensive (!) Baader BBHS mirror diagonals, a SCT to T2 adapter and the Baader quick change adapter. This will require you to also get a T2 dovetail adapter from say Precise Parts for the Denk system but this will give you the shortest possible light path with the system as measured from the SCT visual back, especially with the T2 prism. This is important to keep you from clipping the aperture of the SCT when using the focal reduction side of the power switch plus it brings you closer to the optimum back focus position of the SCT. You may also stand a good chance of reaching focus with the view sans OCS and power switch with the F9 APO but you would need a 2" nosepiece for the Baader diagonal. I find this to be a great low power configuration for my refractors, giving the max FOV available in the 1.25" eyepiece format. Your first view of the double cluster will remove all doubt.
However, you can still use the OCS system with all your scopes with your regular 2" diagonal as well. This is great if you're going to be doing mostly high power viewing during your session. So you have lots of options.
But I'd recommend first hunting down a good used Denk II system (dual arm power switch, OCS and Newtonian extension tube), try it out and go from there. If you don't like it, I've found you can usually sell it for what you paid.