Allen,
Don't own one, but I've pulled a few different ones rented from neighbors - we normally SD with NH3...

If I was to purchase one today, It would be a FAST. It would be equipped with a hydraulic centrifugal through a 3 boom shutoff. Reason 1 for this is if the centrifugal dies, they are relatively cheap to replace - ground-drives are idiot proof for a rental fleet, but are spendy to buy initially and have more moving parts. Reason 2 is that if the controls are run through a Raven (or similar), rate changes can be made from the seat. You may also wish to eventually do some variable rate, or replicated N rate strips in the field (simple as rate 1, rate 2 toggle). Reason 3, is that with 3 boom shutoffs, you can quickly deal with pointrows and part machine widths either manually or with section control.

My coulter selection would be with knives on the back of the coulters. Get the product in the ground, not "point and shoot" - IMO.

Your horse might be a little light for the load depending on topography, but I'd run it with axle duals (as your tongue weight will be significant) and a jag of weights on the nose. It will do a great job, but you might not be running 10 mph uphill with a load on... You can still cover a lot of ground at 6mph x 40' wide.

Ken